Identifying and Managing Sycamore Blight on Sycamore Trees

Identifying and Managing Sycamore Blight on Sycamore Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Do you want the good news of the bad news first? The bad news is that many of our area sycamores are infected with sycamore blight this spring.  The good news is that sycamore blight seldom kills a tree.  Well, it's good news for those of you who like sycamore trees.  Most of you know that sycamores are not my favorite type of tree.  One reason that sycamores don't hold my esteem is that they get sycamore anthracnose .

Sycamore anthracnose, also know as sycamore "blight", is a fungus disease which commonly attacks the leaves and twigs of sycamore trees.  The cool, wet weather this spring has been ideal for the development of this disease.  The fungus survives the winter in cankers (which look like small wounds) on the branch twigs and also on fallen leaves and twigs.  During cool (55 degrees Fahrenheit), wet spring weather, the spores of the fungus develop in these cankers.  The spores are blown and splashed by the rain onto newly expanding buds, shoots, and leaves. The spores germinate and the fungus infects and kills plant tissue.

The first symptom of sycamore blight is usually sudden browning and death of single leaves or clusters of leaves as they're expanding in the spring. It’s easily mistaken for frost or wind injury.

A quick look around the area, and you’ll easily find a large number of sycamore trees that are quite sparse and appear to be leafing out very slowly.  Many of these are affected by “blight.”  As our weather turns warmer (hopefully), the trees will form new leaves but the foliage will not be as dense as in other years.

If our cool and wet weather persists, later leaf infections may also occur.  Symptoms of these later infections appear as brown dead spots which start at the base of the leaf or at avein on the leaf.  The brown spots then follow the veins outward.

Control of anthracnose on susceptible trees is difficult, mainly because of the large size ofmost sycamores.  Recommended cultural control consists pruning off and destroying infected twigs and dead branches and also raking up and disposing of all the fallen leaves and dead twigs.  Both of these actions are designed to remove the organism that lives through the winter and produces spores the next spring.

Spraying with a fungicide to protect expanding buds and leaves from the fungus can be done in the spring as the buds begin to swell andjust start to break open.  This is most practical where trees are young and small enough for you to be able to achieve good coverage when spraying.  Adequate coverage is difficult to achieve on large trees, even for competent applicators with good equipment.  Recommended fungicides are applied at bud‑break and then again at ten to fourteen day intervals during periods of wet weather. Remember that good coverage is essential for effective control.

I should note that sycamore and plane trees vary in their susceptibility to the disease.  Oriental plane trees are resistant while native sycamores are not.  There are some cultivated varieties of Oriental hybrids that are known to be resistant to the disease.  These varieties are "Bloodgood," "Columbia," and "Liberty."   If you must plant a sycamore, plant one of these resistant varieties.

Locust Borer Attacks Black Locust Trees

Locust Borer Attacks Black Locust Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

The locust borer (Megacyllene robiniae) only attacks black locust trees.  It’s a native insect and was first found in the eastern part of the United States in natural stands of black locust trees.  The locust borer caused problems in colonial times by rendering the durable black locust wood unsuitable for use as fenceposts.  As settlers moved west in the country, they brought black locust trees... and the borer with them.  The borer is now found throughout North America.

The adult locust borer is one of the “long-horned beetles” with antennae almost as long as its body.  This 3/4 inch black, slender, elongated beetle is sometimes mistaken for a wasp because of the distinctive bright yellow markings on its back.  Most characteristic is the “W” shaped band across the wings.  The legs are reddish.

As an adult beetle, this pest feeds on goldenrod and other flowers in late summer and early fall.  After feasting on flowers and mating, the female adult beetles lay eggs singly or in small groups in bark crevices, cracks, callus tissue around wounds, and other hiding places on the bark of black locust trees.  Interestingly, this egg laying activity usually takes place from early afternoon to late evening.

In about a week, the eggs hatch into tiny larvae which bore directly into the bark until they reach living tissue.  They spend the winter in the inner bark where they make a small hibernation burrow about one inch in length.  In the spring, they start feeding on the tree in earnest, boring upward and inward towards the center of the trunk.  At some point they make a sharp turn and descend about 3 inches down the trunk within the heartwood.  

They’re apparently good housekeepers, pushing frass and sawdust out of their entrance holes and other openings made for clearing out clogged tunnels.  In the spring, visible clues to their presence are moist areas on the bark, which is caused by sap coming from these opening.  The frass and sawdust materials pushed out of the tunnels and collecting beneath the trees is also a good clue.  They continue boring until the tunnels are three to four inches long and about 1/4 inch in diameter.  The tunnel is oval-shaped to accommodate their round head and the way it eats the wood.  It’s such a good eater, you can actually hear it feeding as it chomps away on the wood.

In mid-summer, the larvae, which have grown to approximately one inch in length, are ready to pupate... the stage where they change from a larva into an adult.  They emerge about a month later as adult beetles.  They exit through the openings they made as larvae.  There is one generation per year.

This past week I have been receiving samples and calls from numerous tree owners and cities in the region who are concerned about the damage from the borer that they’re finding in their black locust trees.  The city of Kahlotus has a great number of infested trees and the city of Richland is faced with the predicament of having 600 to 800 black locusts within their entire park system, with 60 or more in Howard Amon Park alone.  A number of these are badly infested and will probably need to be removed for safety reasons.

What type of actual damage does the borer do?  The beetles primarily attack the trunks and branches of black locust (Robinia psuedoacacia) trees, which are 1½ inches in diameter up to seven to eight inches in diameter, occasionally attacking larger wood.  It usually waits to attack trees until they’re four years of age or older.  Heavy attacks by the locust borer will weaken trees and retard growth.  Severe infestations or repeated attacks can leave wood virtually “honeycombed” and prone to limb breakage during windstorms.  During our last windstorm, a number of badly infested trees lost limbs and branches.

The borer tends to attack stressed trees more heavily.  The first line of defense against this pest is to keep the trees in as good health as possible with adequate watering and fertilization practices.  Usually older trees are not attacked, but when there is a high population of borers or the trees are stressed, the tops of older trees become infested too. 

While the locust borer doesn’t generally kill trees, trees can be killed when the population becomes epidemic in proportion.  Drought weakened trees are especially susceptible to attack.  Soil compaction also contributes to borer attack.  Even pruning creates favorable sites for infestation, since the adult females like to lay their eggs in callus tissue on the edge of wounds.

When the borer is already in the wood there isn’t much one can do in the way of “control” other than pruning out badly infested wood.  Chemicals applied to the bark will not penetrate and kill the larvae.  Systemics applied to the roots for uptake into the plants also don’t get into heartwood and older sapwood tissues where the larva does most of its feeding. 

Any chemical insecticides used for control are applications made to trunks and main branches to prevent reinfestation by young borers in the fall.  Appropriate applications of pesticides labeled for borer control are made in late summer or early fall.  Sprays are targeted at the bark of the trunk and larger branches (greater than one inch in diameter).  The spray applications should thoroughly wet the bark surface.  Special attention should be given to wounds and callus growth where the borers like to lay their eggs.

Heavily infested trees with dying tops serve as “brood” trees for the borer.  It would be advantageous to remove these trees from an area where other, healthier black locusts are growing.  However, the trees should be removed and destroyed during the dormant season when they contain the larvae.  Limbs and branches should also be removed if an attack leaves their wood structurally weak.  These should be removed as soon as the hazard is detected.  When replacing these trees, a community should consider planting a mix of species.  Pure stands or large groups of any one species invites devastation by an insect population or an attack by disease, like the locust borer or Dutch elm disease. 

One of the law’s of nature is “the survival of the fittest.”  This certainly applies to black locust trees.  Trees that are healthy and not stressed will survive; weakened trees will probably end up being dinner for the locust borer and candidates for the chainsaw.  

Fruit Trees Can be a Nightmare for Tri-Cities Gardeners

Fruit Trees Can be a Nightmare for Tri-Cities Gardeners

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It=s a nice dream.... being able to grow fruit right in your own backyard.  However, this dream often turns into a nightmare for many home gardeners who are not aware of how much work it can take to grow acceptable quality worm-free fruit.  It requires regular sprays of insecticides to keep apple and cherry fruit free of worms.  Even if you tire of spraying and are willing to sacrifice your fruit to the Aworms@, residents of Benton and Franklin counties are required by law to control the wormy pests on apples, crab apple, hawthorn, and cherries.   The obstacles to growing backyard fruit trees often leads to many questions from would-be backyard orchardists when they discover that their dreams aren=t easily realized.  Here are some of their frequently asked questions... and answers.

Why do Benton and Franklin counties require me to spray my apple and cherry trees?  Backyard fruit trees, where codling moth and cherry fruit fly are not controlled, serve as a source of infestation for commercial orchards.  Infestations of codling moth and cherry fruit fly in nearby backyard trees mean a grower will have to use more insecticides or additional pest management strategies to control these pests in his orchard.  This leads to increased costs and an increase in the amount of pesticides used.  The infestation may also lead to infested fruit within his crop, which could mean the grower will get less money for his crop or it may even mean he can=t sell it at all.  Because commercial tree fruit production is a significant part of our local agricultural economy, it=s important to keep backyard fruit trees from becoming a liability to commercial growers.

How difficult is it to control these pests? Both codling moth and cherry fruit fly require regular sprays, generally every 7 to 10 days, during the growing season to keep the fruit Aworm free@.

Spraying trees is time consuming ... you have to mix the sprays, apply them, and clean up afterwards including laundering your clothing.  You also need the right equipment for spraying.  If the trees are large, you=ll need more than a hose-end or garden sprayer to reach the tops of large fruit trees.  It=s unsafe to spray fruit trees using a ladder.  You also should wear protective goggles, long sleeves, long trousers, a hat, and shoes when applying pesticides to your trees. These items must be laundered separately from other laundry right after spraying.

The weather can definitely make it difficult to apply the regular sprays needed to keep pests in check.  You should not spray when the temperature is expected to go below 40 degrees when applying dormant oils and you should not spray when the daytime temperature is above 85 degrees when applying sulfur or petroleum-based sprays. Wind can lead to the spray drifting off target, so you should never spray when there=s any noticeable wind.

If I apply a dormant spray, won=t that take care of the wormy pests?  No.  The dormant fruit tree sprays that are applied in the late winter just as buds start to swell are aimed at controlling diseases, not insects.  Dormant oils which should be applied just before the buds open in the spring, only help control certain insects that overwinter on the bark of the tree, such as aphids, scale, and mites.  The dormant oils have no affect on codling moth or cherry fruit flies.

I don=t like using so much pesticide.  Is there any organic way to control these pests?  Some organic sprays are available for codling moth and cherry fruit fly control, but most don=t provide adequate control to keep the home orchard worm-free and most would also require more frequent application.  Codling moth can be controlled without sprays, if you are willing to thin and bag all the apples on a tree using special paper bags. 

I=ve heard about the use of pheromones (insect hormones ) to control codling moth in apple orchards.  Wouldn’t that also work for a backyard orchardist like me?  The lures impregnated with insect sex pheromones are useful tools in codling moth management in large orchards.  The lures are placed around the perimeter of an orchard to confuse male moths looking for a mate.  Unfortunately, the lures have proven ineffective when dealing with small orchards or backyard fruit trees because mated females can come from nearby sources to lay fertile eggs on the apples.  Infested trees close to large apple orchards using lures for codling moth management increase the amount of spraying needed to keep the codling moth out of those orchards.

What about the insect traps advertised in garden catalogs?  Won=t they work in controlling the adult codling moth and cherry fruit flies?  The catalogs may be misleading you.  Codling moth traps are good tools to use to monitor the presence of these pests, but are not effective in eliminating damage because they attract only the male moths looking for a mate.  Again, fertile females can come in from nearby sources to lay eggs.. The yellow color and an ammonium carbonate bate on cherry fruit fly traps are what attract both male and female adult flies.  However, the traps are not considered adequate for good cherry fruit fly control.

Is diazinon still available to home gardeners to use on apples and cherries?  What pesticide can I use to control codling moth and cherry fruit fly?  There is still a number of home garden diazinon products commercially available that can be used on backyard cherry trees but only a few products are labeled for use on apples.  However, these products may not be readily available at your local garden store.   If you find a home garden product containing diazinon, be sure the label says it can be used on the type of fruit tree you have.  It is illegal to use the product on cherries or apples if they aren't listed on the label.

You may want to look for a home garden insecticide product containing a combination of malathion and methoxychlor for use on apples.  There are quite a few of these labeled as Afruit tree spray@ or Ahome orchard spray@ and most also contain a fungicide, captan, for disease control. 

Why shouldn’t I grow hawthorns and crab apple?  Their fruit also becomes infested with codling moth and can pose the same threat as infested apple trees do to commercial orchardists.  If you have a hawthorn or crab apple in your yard and it=s infested with codling moth, you must spray it regularly.  

How about ornamental flowering cherries?  Are they a problem for commercial growers?  Your ornamental Japanese flowering cherries don=t produce fruit and shouldn’t pose a threat to commercial cherry growers.  However, sometimes the rootstock from below the graft of a flowering cherry starts to grow.  It will usually be a cherry that produces fruit.  These shoots from the understock should be removed when they appear.  If the understock is the only part of the tree that=s still alive, then the entire tree should be replaced. 

Since apples and pears require so much spraying to keep them worm free, are there any other types of fruit trees I can grow without a lot of spraying?   There are no common wormy pests of apricots, peaches, nectarines, and plums that require regular spraying of the trees.  Your best bet is to grow plums, they don't require regular spraying and have a more reliable crop than peaches or apricots.

Verticillium Wilt, A Disease That Attacks Trees From Inside Out

Verticillium Wilt, A Disease That Attacks Trees From Inside Out

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It’s a disease that becoming more of a problem in our region.  Its name is verticillium wilt.  Verticillium wilt is a fungus disease that attacks over 300 woody and herbaceous host plants.  While it can be a problem in the vegetable and flower garden, its attack of woody plants is what creates the most havoc for home gardeners. 

Imagine a lovely, healthy maple tree in your front yard... growing well with the proper watering, fertilization, and good care that you’ve provided over the years.  One summer half the tree suddenly wilts and dies.  This scenario could happen if your tree is attacked by verticillium wilt.

There are lots of tree species it can attack, but there are some that it commonly attacks in our region.  These are maple, ash, catalpa, redbud, smoke tree, sumac, and Russian olive... with maple being the tree most often attacked.

Verticillium wilt fungus is a sneaky disease, entering a plant through the roots in the soil.  Infections are not obvious like some other diseases, such as powdery mildew or sycamore blight.  Symptoms can be acute... with leaf curling and drying, abnormal red and yellow coloring of the leaves, partial defoliation, wilting and dieback of branches.  This wilting and dieback will typically develop on one main branch, a sector of the crown, or an entire side of the tree.  Chronic symptoms are stunted growth, yellowish leaves, crispy brown edges on the leaves, slow and stunted growth, heavy seed crops, and branch dieback. 

Trees with verticillium wilt may limp along for years, exhibiting symptoms some years and other years not showing up at all.  However, the disease can suddenly attack a completely healthy tree causing it to wilt and die in a short period of time.

The first outward symptoms of verticillium wilt are leaf scorch, abnormal coloring, and dieback of branches.  However, there are many things that cause the same symptoms.  Girdling and encircling roots, root and crown rot, drought stress, compacted soil, trunk injury, and improper planting can all cause similar symptoms.

When verticillium wilt is suspected, a pocketknife should be used to make a slanted cut on an affected branch.  When verticillium wilt is present the cut may reveal streaking or discoloration of vascular tissue (transport) tissues in the wood.  In some species, like maple, this streaking is olive-green, but it varies from tan or brown to green or even black in some species. 

What causes this streaking?  The verticillium fungus once inside a tree, invades the xylem which is the water conducting tissue in roots, trunks, and branches.  The fungus produces toxins that can kill cells, even cells not close to the infected tissues.  The disease spreads in the plant by spores.  New fungal spores move upward with water in the vascular tissue.  The spores then lodge in healthy vascular tissue and new infections begin.  Dead and discolored tissues develop at the sites of these infections, first appearing slightly discolored and then developing the characteristic color for the species.  It’s this discoloration that causes the diagnostic streaking in vascular tissue.

The infected tree reacts to this fungal invasion by trying to block its spread.  It does this by producing gums and tyloses (chemical substances) in the vascular tissue to block fungal movement.  However, these gums and tyloses also impede the flow of water.  This results in the external symptoms of verticillium wilt that can be confused with other causes that also deter a tree’s uptake of water.

When looking for streaking in a recently wilted branch, the first place to look for streaking is directly under the bark.  If no streaking if found there, a deeper into the sapwood may reveal streaking.  However, streaking may not be evident even if the plant is infected with verticillium wilt.  It typically is not present in recently infected sapwood and is usually not found in twigs of one inch in diameter or smaller.  Streaking will most likely be found near the base of the tree, since the initial infection route is usually through the roots.  As you move up the tree, you’re less likely to find streaking.  To make diagnosis even more difficult, there is no detectable streaking of vascular tissues on certain species, like ash.

Before we talk about management of verticillium wilt, let’s talk a just a little more about it’s life cycle and how it enters a tree.  The wilt’s microsclerotia, which are tiny black resting structures, can be found in many soils.  They spread by wind or water.  They can also be introduced into “clean” soil from contaminated seed and plants or from contaminated soil on root balls, hand tools, or machinery.  They can exist in the soil for many years, up to 15 years, without contact with a host plant.  Lying in wait, the microsclerotia will germinate and infect a new plant when they come in contact with the roots of a susceptible host.  They invade the roots through a wound or by direct penetration.  Once inside the host, the fungus gets into the vascular tissue and spreads throughout the plant by spores. 

So how do we control the disease?  Plain and simply, you can’t control verticillium wilt once a tree is infected.  No fungicides have been found to be effective against the fungus in trees.  Injections of fungicides into a tree have been tried, but the results have been inconclusive.  You may not be able to control verticillium wilt, but you can try to manage it.  Just because a tree is infected, doesn’t mean it will die.  It may recover and be able to live with the disease... with careful management.

Trees should receive plenty of water to promote growth and avoid stress.  Infection is less severe when trees are not drought stressed.  A good deep soaking once a week during hot summer weather will help.  Fertilization with ammonium sulfate, when symptoms are first noticed, is recommended by many “verticillium wilt” experts.  Research in Michigan indicates that you should avoid applications of nitrate fertilizers because they ineffective in management of the disease.  While fertilization is part of the management program, you should avoid excessive fertilization, which apparently can increase problems with the disease.

You will want to promptly remove branches killed by the disease but you shouldn’t remove them until you give the water and fertilizer a chance revive recently wilted branches.  If they don’t come back in response to the extra care, remove the branches, cutting well below any of the streaking or discoloration and back to a main branch or limb.  Be sure to make proper pruning cuts and don’t leave stub cuts.  In between cuts, disinfect your pruning sheers with 70 per cent rubbing alcohol or a 10 per cent bleach solution.  Wood from infected branches should be removed and destroyed.  Chipping the wood and using it for mulch can spread the disease to other areas.

If a tree dies and needs to be replaced, keep in mind that the microsclerotia can remain in the soil for over 15 years.  When replanting, select a species of tree that is resistant to the disease.  Trees reported to be immune or resistant to verticillium wilt include beech, birch, ginkgo, honeylocust, sycamore, hophornbeam, sweetgum, pear, mulberry, apple, hawthorn, willow, white oak, bur oak, and sycamore.  Dogwood and linden appear to be susceptible to some strains of verticillium and resistant to others.  Fir, spruce, pine, juniper, and arborvitae are also resistant.

Sycamore Problems

Sycamore Problems

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

Lace Bugs

Just this past week, several people have brought me samples of ailing sycamore trees.  On each of these samples there were two problems worth mentioning.  One problem was an insect, the sycamore lacebug.  It’s a tiny bug with lace-like wings.  It sucks sap from leaves creating a speckled appearance. The lace bugs can be found on the undersides of leaves along with small black specks of their excrement.   When feeding is severe, the leaves take on a brownish or dry look. 

The lace bug has not become a serious annual problem on sycamores, but it does show up from time to time.  The amount damage it causes is typically insignificant and tends to only become extensive in late summer or early fall.  With damage occurring so late in the season, control is not needed.

Herbicide Injury

The other problem evident on these samples was more noteworthy.  The leaves were somewhat malformed and cupped downward with an excess of the leaves’ natural hairy fuzz.  This is a sure sign of herbicide injury.  It was very likely caused by applications of “weed and feed” products to the lawn.  Dicamba or 2,4D, commonly found in “weed & feed” products, were probably the herbicides at fault.  Sycamores are particularly sensitive to damage from these two herbicides.

The downward cupping of the leaves is not critical. After all, the tree will soon be losing these leaves in preparation for winter.  The real damage from these lawn herbicides happens to the trunk of the tree.  Both herbicides can lead to damage of bark tissues and the emergence of bark eruptions on the main trunk, usually more extensively on the lower portions of the trunk.  The bark loses its beautiful mosaic pattern and smooth appearance.  It becomes rough and fissured.  Immediately beneath the eruptions, the bark tissue is pink and spongy.  Beneath the eruptions, the inner wood becomes dark brown.  This damage may later attract a borer, the American plum borer, which then causes even greater damage to the bark and trunk tissues.

Dicamba and 2,4 D can cause damage to sycamores even when applied at the correct rate, but greater damage occurs if they’re over-applied.  Over-application often occurs when home gardeners don’t calibrate their drop-spreader or sprayer before applying a “weed and feed”.  As a rule, 2,4 D and dicamba should not be applied in a general application to the lawn over the root zone of sycamores.  Spot treating weeds is safer for the sycamores and more economical.

Leaf Scorch

Yet another problem being noted by some sycamore owners is leaf scorch.  This shows up as bright yellow to brown leaves scattered throughout the crown and accompanied by substantial leaf loss.  The leaves most severely affected are the oldest... especially the inside leaves.  The most likely cause of this problem is heat and drought.  It’s been a hot summer.  Sycamores are big trees and if they don’t get enough water they let you know.  Lack of deep watering, girdling roots, and compacted soils can all be factors in a sycamore becoming drought stressed.

Mulching Trees is Good and Bad

Mulching Trees is Good and Bad

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It seems to be human nature... if something is good, a lot is even better.   Unfortunately, that’s not always the case.  For example, one of the best things you can do for the trees in your yard is to mulch them with an organic mulch.  Excessive amounts of mulch applied improperly by enthusiastic gardeners can cause more harm than good.  I want to talk about the problems caused by excessive and improperly applied mulch.... but first let’s review the benefits of mulching along with the proper way to apply mulch.

Benefits of Mulching

Competition with Turf  —  Trees and turf are competitors that don’t get along particularly well.  They compete for the same water and nutrients that are available in the top foot of soil. Because grass roots colonize faster and take up more of the soil space, they often “win” the fight for nitrogen in the soil.  Both struggle against each other for the available water. They also compete for light, with trees having the uncontested advantage because of their height.  As they get taller and wider, trees intercept so much light that the grass growing in the tree’s shade can’t get enough light.  As a result the grass thins out.

Grass has a secret weapon in its fight against trees. Grasses apparently release antagonistic chemicals into the soil that slow the growth of tree roots. This phenomenon is referred to as allelopathy. Researchers have found that tree growth is reduced when trees are grown in turfed areas compared to trees with mulched root systems. They attribute the improved growth of mulched trees to the absence of these antagonistic chemicals along with the other benefits provided by mulches.

A layer of mulch over the entire root zone of trees reduces the contentious competition between trees and turf... allowing both to grow better in peace.

Conserving Moisture  —  Mulching conserves moisture by reducing the amount of water that’s lost through evaporation from the soil surface.  A layer of mulch reduces the amount of water that must be applied by irrigation.

Adds Organic Matter to Soil  —  As organic mulches decompose they improve soil fertility and structure.  Decomposing organic mulches also provide food and a favorable environment to beneficial soil organisms, such as earthworms and “good” fungi.

Provided Insulation  —  A layer of mulch acts as insulation for tree roots, protecting them from extreme summer and winter temperatures.

Discourages Weeds  —  Mulches discourage weeds, which also compete with trees for water and moisture.

Reduces Soil Erosion  —  Mulches reduce soil erosion and soil compaction, as well as improving water entry into the soil.

Protects Trunk  —  A circle of mulch around a tree decreases the chances of damage to the tree trunk from string weed trimmers or mowers.

Looks Nice  —  An attractive layer of mulch around trees and shrubs provides a more uniform look to a landscape.

The Proper Way to Mulch

So just what is the “proper” way to mulch trees?  Proper mulching involves applying a two to four inch layer over the area around the trunk, extending out to the dripline or beyond.  The larger the area, the more beneficial to the tree. The ideal way of mulching is to apply mulch over the entire root system... which can be an area as much as two to three times the spread of the branches and extending well beyond the dripline.  The practical way of mulching is to apply mulch to an area at least four to five feet in diameter around the trunk.  However, it’s very important to keep the mulch six inches away from the trunks of young trees and one foot away from the trunks of older, mature trees.

A well-aerated, composted organic mulching material is best for properly mulching a tree.  Some of the preferred materials for mulching trees include bark, grass clippings, shredded leaves, and pine needles. If grass clippings are used they should be mixed with some coarser materials to discourage matting.  Wood chips make especially good mulch if they’re composted first and then mixed with leaves and bark.  Fresh wood chips and sawdust should never be used because their decomposition ties up available nitrogen in the soil, depriving the growing tree of nitrogen needed for growth.

Improper Mulching Can Kill Trees

Improper mulching or mulching mistakes are easy to make. One of the most common mulching mistakes is over-mulching.  Too much of a good thing isn’t better... in this case it can kill trees by suffocation.  When too much mulch is applied, it limits the amount of oxygen that’s getting to the roots of the tree. The excessive mulch also slows evaporation of soil moisture and the soil stays wet for long periods.... exacerbating the lack of oxygen in the soil.

Another common mulching mistake is placing the mulch against the trunk of the tree.  The base of the tree where the trunk flares out must be able to “breathe” .  It’s not root tissue and can’t tolerate a continually moist environment or a lack of oxygen.  Frequent irrigation that keeps a tree trunk saturated, a change of grade that buryies the flare, or mulch applied directly to the base of a tree can cause the death of the inner bark.  When the inner bark dies, the tree is no longer able to send food to its roots and the roots eventually starve.  Without roots that can take up water and nutrients, the tree dies. Excess moisture at the base of the tree can also favor bacterial and fungal diseases that attack and kill inner bark tissues. 

A very thick a layer of materials that are not fully composted, such as a thick layer of green grass clippings, can also lead to trouble.  This thick layer may actually heat up and go through the composting process, much like a compost pile.  The heat of early decomposition may lead to temperatures as high as 120 to 140 degrees in the mulch layer.  If this “composting” mulch is directly in contact with roots or trunk tissues, these temperatures can kill them.

Excessive insulation from a very thick layer of mulch can delay the hardening process in the fall, making a tree more susceptible to winter injury from cold temperatures, especially those occurring early in the winter.

When mulching was first advocated, some enthusiastic gardeners applied thick layers of mulch to their trees.  They later found that as a result of this thick layer the tree roots grew close to the soil surface... probably because they needed air.  These shallow roots didn’t have problems until severely cold temperatures arrived, killing them... and the trees.

Finally, a more recent and interesting way to improperly mulch trees are with mulching “volcanoes.” Mulching volcanoes occur when gardeners apply a tall pile or mountain of mulch (or sometimes soil) around the base of the tree.  These do nothing to help a tree... and are an easy way to kill it through suffocation and collar rot. 

So remember... mulch is very good for trees, but a lot of much mulch or mulch that’s applied improperly is bad for



When Snow or Ice Bows and Breaks Tree

When Snow or Ice Bows and Breaks Tree

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Heavy wet snow, freezing rain and ice can mean bowed and broken tree limbs and trunks.  What causes limb and branch breakage?  Certain types of trees, especially fast growing species, have "brittle" wood that is prone to breakage.  This includes Chinese elm, silver maple, boxelder, and poplar.  Some tree species have narrow branch angles, making them structurally weaker in situations like these.  The `Bradford' cultivar of callery pear is a good example of a tree with a weak structure due to narrow branch angles.

Another reason for structural weakness in a tree is past pruning practices.  Improper pruning practices, such as topping or stub cutting, leads to the development of poorly attached branches.  There is a great tendency for these branches to break off the tree as they grow larger and heavier, especially when stressed by strong winds or a load of snow and ice.

Trees also become structurally weaker when wood rot develops in the trunk and main branches.  Wood rot is the result of fungi, which invade the tree after physical damage occurs... through wounding, bad pruning cuts, and severe temperature damage.  Severe wood rot can develop through repeated wounding and large branches that have been topped.

Some trees broke under the recent heavy snow-loads but some only bent... bending or bowing was common on young deciduous trees, as well as on certain types of evergreens trees and shrubs.  The wood in these plants is more elastic, with wood bending instead of breaking.  In these cases, it was merely a factor of the snow and ice and the branches yielding to the weight.

Now what can be done about the injured trees and shrubs?  Let's deal with the "bent-out-of-shape" plants first.  According to Dr. Ray Maleike, Washington State University Extension Horticulturist Emeritus, "When snow or ice bend branches and entire trees out of shape, the offending snow or ice should be removed immediately and an attempt made to straighten the bent branch or trunk.  If the plant part isn't straightened very soon after the snow has stopped, the plant may remain bent over... permanently."  Collected snow can be removed with a broom.  Sweep upward to lift the snow off.  However, don't disturb the branches if they're heavily weighted and brittle with ice or you have a concern about the structural integrity of your tree.

Maleike suggests trying to physically straighten the plant or branch once you remove the snow.  He notes, "This doesn't always work, but it does occasionally.  If the young tree or shrub has been squashed down to where it extends into traffic areas, it may have to be pruned."

Around our area there a number branches on multi-stemmed, columnar-needled evergreens, like arborvitae, that have been bent out away from the plant.  Maleike indicates that these may be tied back to the main plant with a soft, non-chafing material like cotton clothesline or nylon pantyhose.  The tying materials may have to be left on for 6 months or more.  He notes, "Tying the plants together before the winter starts is a good preventative for this problem."

What can be done for small trees which have bowed over but have not broken or cracked?  These trees can be staked until they can stand on their own again.  Maleike recommends this procedure, "Drive two stakes, about six to eight inches away from the trunk, into firm ground. (Be careful not to severe major roots.)  Then tie the trunk to the stake at the lowest height, which stabilizes the tree in an acceptable upright position.  A nonchafing tying material must be used."

The stakes should not be left on indefinitely.  They should be removed as soon as the tree can stand by itself again.  This should be within the first growing season after the "bowing" occurred.

Trees with broken branches don't need immediate attention.  However, it's advisable to prune off broken branches as soon as the weather and circumstances allow.  Prune damaged branches back to another branch or the main trunk if necessary... don't make flush cuts and don't leave branch stubs.  On large branches this cut should be made to just outside the branch collar.  Be sure to follow recommended tree pruning practices.  When power lines, large limbs, or main branches complicate the matter, contact a trained and certified arborist.

With the breakage of limbs, sometimes bark is torn on the larger limbs or the main trunk.  To help the tree, the torn bark should be carefully trimmed with a sharp knife to make a smooth, rounded edge to the wound.  Cut only the bark and not into the wood.  No wound dressing materials are recommended for bark wounds or pruning wounds.

New Ways to Control Worm Pests in Fruit Trees

New Ways to Control Worm Pests in Fruit Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

If you own an apple, crabapple, pear or fruiting cherry tree, you may be wondering what to do about controlling worms in the fruit.  With apple, pear, and crabapple, regular sprays are needed to prevent the codling moth larvae from boring into and destroying the fruit.  These sprays start not long after full bloom and continue until close to harvest.  With cherries, regular sprays are needed to control the cherry fruit fly to prevent the cherry fruit fly from laying its eggs under the skin of developing cherries.  The eggs develop into those nasty Aworms@ or maggots found inside a cherry, destroying its palatability and storage life. The sprays for control usually start in mid-May and continue until close to harvest.

Because residents of Benton and Franklin counties live in a region with an important commercial tree fruit industry, they=re required by county law to control these wormy pests in any fruiting apple, crabapple, pear, or cherry trees on their property.   Infested backyard trees are a source of contamination for any nearby commercial orchard.  This can lead to commercial orchardists having all their fruit rejected by a packing house and the need to apply pesticides more frequently to keep their fruit worm free. 

Limited Pesticides Available to Prevent Wormy Fruit

Even responsible home gardeners are having an increasingly hard time controlling these wormy fruit pests.  The reason is that there aren’t many effective chemicals still available to home gardeners for use on fruit trees to control these pests.  In past years, weekly sprays of diazinon would control them, but diazinon will not be available after this year.  The limited diazinon products still available have very restrictive labels, limiting the number of times they can be applied to fruit trees during the growing season.

There are only two home garden products labeled for use in Washington containing combinations methoxychlor and malathion, two insecticides that can be used on apples and cherries for effective control of codling moth and cherry fruit fly. They are Ortho=s Home Orchard spray and True Value=s Greenthumb Liquid Fruit Tree Spray.  These may be difficult to find, but are available.  Methoxychlor-malathion mixes will provide adequate control when applied every 7 to 10 days.  There are also several products that contain malathion without methoxychlor and should also provide adequate control.

Clay Deters Codling Moth

One non-chemical material that can be used by home gardeners is a product called Surround.  Surround consists of highly refined kaolin clay.  Mixed with water, it=s sprayed onto trees.  The white clay particles coat the leaves and the fruit.  Researchers have found that rather than killing pests, this material acts as a repellent or deterrent to insects.  Insects do not like the coated surfaces and fail to deposit many, if any, eggs on the treated surfaces.  With some insects, the kaolin coating may simply hide the host plant from an insect=s chemical receptors, preventing the pest from finding the plant.

Unfortunately, while Surround has been extremely effective in repelling some pests, it=s not completely effective against codling moth, only reducing codling moth damage between 30 and 90 per cent from untreated controls.  Even if it was completely effective, home gardeners might not find treated trees aesthetically acceptable since the treated trees are coated with a chalky white coating, giving them a ghostly appearance.  In addition, the harvested fruit requires thorough washing to remove the kaolin coating.

One Product Not Available to Home Gardeners

University researchers and chemical companies are searching hard for effective materials to help control pests with less chemicals and less impact on the environment and beneficial insects.  One new product that has been developed is ALast Call@.  This is a paste that=s applied from a custom dispenser as droplets about the size of a small pea onto the trunks and main branches of each apple tree in an orchard.

ALast Call@ contains permethrin (an insecticide), a UV protectant to keep the material from breaking down too quickly, and an insect pheromone (sex attractant). The material is designed to attract the male moths to the droplet and then kill them.  After contacting the droplet and finding out it=s not a sought-after female moth, a male moth becomes paralyzed and quickly dies. ALast Call@ must be applied before the male moths have a chance to mate with the females.  That=s because the females aren’t attracted to the pheromone droplets.  Once they=re fertilized by the male moth, they start laying eggs... leading to fruit damage. Once the females are laying fertile eggs, it doesn=t matter if the males are dead or alive.

While ALast Call@ has provided positive results in commercial orchards, in a Utah State University research study it proved ineffective in controlling codling moth in home orchard sites.  The reason for this failure was probably due to fertilized females from outside sources (such as nearby unsprayed, infested neighborhood trees) depositing eggs on the treated trees.  Remember that ALast Call@ doesn’t harm the females, just the males.  ALast Call@ may become available to home gardeners in Washington as early as this year, but some regular pesticide applications will probably still be necessary to adequately control codling moth when it=s being used.

One New Produce Provides Some Control

Spinosad is another new insecticide product.  It=s made from two spinosyns.  Spinosyns are naturally derived chemicals with insecticidal activity.  The spinosyns were supposedly discovered in 1982 by a scientist who was vacationing in the Caribbean.   The scientist collected soil from an abandoned rum distillery and discovered a new bacteria, named Saccharopolyspora spinosa, in the soil.  (That sounds like an odd vacation even for a scientist.)

This newly discovered bacteria produced metabolites from the fermentation process that were found to have insecticidal properties.   New insecticides, spinosyns, were derived from these metabolites.  The spinosyns act on an insect=s nervous system, causing hyperactivity, paralysis, and death in a relatively short amount of time.  It sounds a bit gruesome, but they=re very effective on some insects and they have extremely low toxicity to humans and animals.  Spinosad, formulated in 1988,  kills a variety of pests, including codling moth, but doesn=t harm many beneficial insects.  Spinosad provides moderately good control of codling moth on apples, but does not provide adequate protection when infestations are heavy.

How about Traps?

If you open a garden supply catalog you may see insect traps recommended for control of codling moth or cherry fruit fly.  These traps really only help tell you when these pests have emerged and help you in timing any control spray applications.  Traps for codling moth only attract the male moths, leaving fertile females to lay their eggs without impunity.  Yellow sticky traps catch both male and female cherry fruit flies, but they only trap some of the flies.  The don=t catch the majority of flies and are not effective controls. 

The Bad News

The bad news is that there are fewer and fewer tools available to home gardeners for controlling codling moth satisfactorily.  While there are some newer, less toxic materials and methods available now and on the horizon, they currently don=t promise to totally prevent damage from infestations.  If planting a fruiting apple, crabapple, pear, or cherry tree, one might even want to ask if it=s worth the trouble... considering the difficulty, time and expense involved in controlling these pests.


Avoid Spreading Disease by Pruning

Avoid Spreading Disease by Pruning

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

What’s your favorite type of pruning tool... a pair of ratchet hand pruners, a lightweight pair of loppers, or a handy folding pruning saw?  Tools like these are standard equipment for gardeners who have a lot of trees and shrubs in their landscape.  They’re needed to prune off ill-placed branches, remove older wood, and eliminate any dead or diseased portions of a plant.  Removal of these infected tissues is very important in preventing the spread of disease.  However, many of us home gardeners may actually be spreading disease if we’re not disinfecting our pruning tools between cuts.

How can pruning tools spread disease?  According to WSU Plant Pathologist, Dr. Warren Copes, if you cut through a section of stem where a pathogen, such as a virus, bacteria, or fungus is present, then the parts of the pathogen may adhere to your pruning tool. When certain diseases are suspected, it’s a good idea to disinfect your pruning tools after every cut.

Copes also points out that not every dead branch is the result of an infection by a disease.  There are also cultural and environmental problems that can lead to dieback.  Let’s look at some common diseases that cause problems in our area and the “protocol” suggested for disease management through pruning and disinfecting the tools we use.

When we have cool, wet springs, a common problem in this area is sycamore anthracnose, also known as sycamore “blight.” True to its name it attacks sycamore trees.  This fungus disease causes cankers or lesions, which eventually girdle a stem and lead to the death of tissues beyond the canker. Over time, repeated infections create sycamores with unsightly crowns.

Where practical, it’s recommended to prune out the cankers caused by the anthracnose fungus.  This improves a tree’s appearance and more importantly removes a source of future infections.  Cuts should be made four inches below any discolored wood.  The disease is spread primarily by wind and rain, not by pruning equipment.  With this disease, you don’t need to disinfect pruning tools after cutting off infected tissue.

One fungus disease that we’ve seen quite a bit of this year is verticillium wilt fungus.  Unlike sycamore anthracnose, verticillium wilt is distributed within a plant at considerable distances from the area of obvious dieback.  It usually enters the plant by way of the root system and moves through the vascular system to plant tissues.  Dieback of branches and limbs is caused by impairment of the root system and the plugging of the vascular system... the system that transports water and nutrients within the tree.  In our region, verticillium wilt is a common problem on maple, ash, sumac, redbud, catalpa, Russian olive, and smoketree. However, there are many other types of trees, shrubs, and garden plants susceptible to verticillium wilt.

While the verticillium wilt fungus can travel throughout a tree, it’s usually not evenly distributed in the plant.  Copes points out, “Since the pathogen isn’t evenly distributed, it’s difficult to identify where the pathogen would be located and also why the fungus is not always spread on pruning tools.”  Dead portions of trees infected with verticillium should be pruned out, but we must keep in mind that this doesn’t remove the pathogen which is located in the roots.  Pruning tools used on trees that have been diagnosed with verticillium wilt or are suspected to have it, should be disinfected between trees and when you are done pruning.

Some “blights” or diseases are caused by a bacterium rather than a fungus.  The most common one that can cause problems in local landscapes is fireblight,  Erwinia amylovora.  Fireblight attacks many members of the rose family including apple, flowering crabapple, pear, pyracantha, hawthorn, cotoneaster, quince, and mountain ash.

Symptoms of a fireblight infection usually start in the spring with infected flowers appearing water soaked.  The flowers may turn brown to black and fail to fall from the tree or shrub.  The bacteria moves down the infected blossom into the twigs, resulting in the sudden death of other flowers and fruits on the same twig.  Often, the twigs will develop a hooked tip or"shepherd’s crook."  Twigs and leaves look almost black, as if scorched by fire.  As the bacteria moves down a twig into a branch, the tissues darken and die. If the outer bark is cut or peeled away, the inner tissues will appear red and water‑soaked.

Fireblight infections commonly occur in the spring when bacterial strands from dead infected tissues are splashed to flowers by rainfall or irrigation water.  The bacteria may also be spread to the flowers by insects that have visited infected plants.  Fireblight often enters a plant through natural openings in the floral parts.

Infection is favored by wet weather and temperatures between 65 and 86 degrees Fahrenheit.  Because of the relatively low rainfall conditions in this region, fireblight is not often a problem in home landscapes.  However, in some years the spring moisture and temperature conditions are just right.  This past spring’s weather provided perfect conditions for fireblight infections in a number of home landscapes.

Once an infection is noted in a plant, it’s important to prune it out immediately.  Pruning cuts should be made at least 12 inches below any discolored wood.  This is because discoloration is a chemical response by the infected plant.  It takes a while before the discoloration forms in infected wood. 

This rule of pruning at least 12 inches below discolored wood can cause a dilemma.  Copes notes that, “Sometimes, a blighted twig or spur may be less than 12 inches away from a larger limb and such removal would disfigure the tree.  In this case, there is no easy answer. Removing the scaffold limb may be necessary.”  If you don’t remove the limb, you should monitor the tree to see if the disease is still present.  While 12 inches is the rule, the disease doesn’t always follow the rules.  It may be present further down, especially if there is a length of time from the first appearance of symptoms and the removal of infected wood.

Pathologists have not been able to confirm that contaminated pruning tools actually spread fireblight from one plant to another.  However, the accepted practice when pruning off fireblight infected wood is to disinfect pruning tools after each cut.

Now we’ve talked about when you should disinfect your pruning tools, but just how should the tools be disinfected?  Plant professionals use a variety of materials to disinfect their pruning tools including commercial horticulture products and also other chemicals.  An article on disinfecting horticultural tools is available from University of Florida IFAS Extension at:

Be aware that some disinfecting chemicals are corrosive.  Make sure to wash the chemical off after the final disinfecting, allow the equipment to dry thoroughly, and then coat the metal parts with light oil or a silicone based spray.  If viruses are the suspected disease, clean your tools by washing them with detergent to physically remove the virus and inactivate virus that may remain on the blades.


Managing Mite Problems

Managing Mite Problems

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It might be mites, it might not.  Spider mites are often blamed for plants turning brown evenwhen they=re nowhere to be found on a failing plant.  How can you tell if your tree, shrub or garden plant has mites? 

What are Mites?

Spider mites are not insects.  They=re tiny arachnids related to the other arachnids that we know and Alove@, includingspiders, ticks, and harvestmen (daddy longlegs).  Like their relatives, spider mites have eight legs and lack wings, antennae and compound eyes.  Members of the insect family typically have six legs, antennae, compound eyes and wings.

Spider mites are visible, but extremely small (1/60th of an inch in length or smaller) and almost microscopic. One way to tell if a plant has mites is to tap a branch or some leaves suspected of having mites over a piece of white paper.  Invariably, little dust specks will fall onto the paper.  If after a second or two the little specks start crawling, it=s a good bet that they=re mites.

The other way to detect a mite problem is to look for their damage and other signs of their presence.  Spider mites don=t have chewing or piercing-sucking mouthparts. To access plant sap they pierce and rupture leaf cells with needle-like stylets.  They then suck up sap that seeps out of the punctured cells. This type of damage leads to the death of individual cells, giving the leaf a finely stippled appearance. As the damage increases a leaf appears discolored, then it turns yellow to brown and dies.  Some types of mites even inject a toxin when they feed which can lead to leaf distortion.

Another sign of a mite infestation is webbing.  The webbing is very fine and, depending on the type of mite, is often found on the undersides of leaves.  It shouldn=t be confused with more visible webbing made by spiders or the cottony masses from cottonwood and poplar trees.  However, it=s important to note that not all spider mites produce webbing... so you can have a mite infestation without webbing.

Mite Life Cycle

Knowing the life cycle and habits of a pest enables us to better manage that pest when it becomes a problem.  Because the two-spotted mite is the most common spider mite that causes problems for trees, shrubs, garden flowers, and vegetables let=s take a look at its way of life. 

The two-spotted spider mite, thus named because of the two dark spots on the back of the adult mite, start out as an egg.  The egg hatches into a larva that has only six legs.  This larva molts into a nymph with eight legs. The nymph molts into a larger nymph and then becomes an adult.  Both the larva and the nymphs resemble the adult.  This entire process takes about five to 20 days depending on the weather.  When winter comes, many types of mites overwinter as eggs. However, the two-spotted mite overwinters as an adult in the soil or in bark crevices on trees and shrubs.  They become active as soon as plant growth begins in the spring.

Mite Build-Up

During hot weather, two-spotted mite populations can build up quite quickly causing plant damage.  A female two-spotted spider mite lives approximately 30 days and lays about 100 eggs. One reason that hot weather leads to spider mite explosions is because of the low humidity.  With low humidity the excess water they excrete evaporates more rapidly.  This allows them to feed more heavily, favoring reproduction.  Another factor is that many of the natural mite predators are stressed by the hot, dry conditions and aren=t able to multiply quickly enough to keep up with the burgeoning mite population.

Hot weather doesn’t=t favor all types of mites. One very notable exception is the spruce spider mite that feeds on conifers, especially spruce and juniper.  This mite is most active during cooler spring and fall weather and actually goes dormant (in an egg stage) during hot summer weather.

Natural Mite Control

Spider mites do have some natural enemies.  They=re Adinner@ for predatory insects, such as dark- colored lady beetles, lacewings, predatory thrips, minute pirate bugs, and big-eyed bugs.  There are also a number of predatory mites that feed on spider mites and keep their populations under control especially when the weather isn=t extremely hot and dry.  One reason for spider mite outbreaks when the weather is not hot is that these predatory mites are killed off when insecticides are applied to plants.  They=re particularly sensitive to carbaryl (Sevin), but may also be harmed by other insecticides.   To keep spider mites in check, avoid using pesticides that kill off predators.

Controlling Mite Infestations

One cultural technique that helps keep mite populations in check is periodically syringing mite-prone plants with a forceful spray of water.  This forceful spray not only knocks off and kills the spider mites, but also dislodges the webbing that collects dusts and deters the natural predators.  It=s also important to keep plants from becoming drought stressed in hot weather.  Plants under stress are more vulnerable to spider mite attack.

If cultural controls don=t work, then pesticide sprays may be needed if significant damage is showing up on your plants.  Since mites aren’t=t insects, most garden insecticides are not very effective.  There are specific miticide chemicals for mite control, but they=re not readily available to home gardeners.  Two options that are available are insecticidal soaps and horticultural oils.

Insecticidal soaps are only moderately effective against mites.  For best results good coverage to both the upper and lower leaf surfaces is essential.  (Remember most mites are on the bottom of the leaves.)  The soap is only effective on the mites that are contacted with the soap spray.  Eggs are not harmed, so repeat applications are usually needed within seven to ten days in hot weather. Additional retreatments may be needed. 

During the growing season horticultural oils may be applied at the summer rate... but be sure to check the label for any hot weather precautions.  Horticultural oils may also be used on dormant plants in the spring at a dormant application rate for controlling overwintering adult mites and mite eggs. 

Spider mite infestations are not as common as some gardeners think.  I sometimes see infestations of spider mites on willows, marigolds, roses, and impatiens.  Spruce spider mites are occasionally a problem on area junipers and spruce, especially dwarf Alberta spruce.  I very seldom see spider mites on arborvitae or other landscape and garden plants.  So if your plants start to turn brown, check for stippling, crawling specks of dust, and very fine webbing on the undersides of leaves.  If in doubt, take a sample to your local Master Gardener Plant Clinic



Fall and Winter Watering

Fall and Winter Watering

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

When irrigation water is turned off and systems blown out in the fall, your landscape plants still need water.  Foggy mornings, heavy frost, and cloudy skies often give a false impression that plants have adequate soil moisture.  Relatively dry air and low or no measurable precipitation lead to dry soils.  This means that even in the fall and winter... trees, shrubs, and lawn grasses need water to avoid drought stress.  This is particularly true during the fall and early winter when there is little or no snow cover... or when there is an extended warm fall.

Fall and winter watering can be crucial to having healthy plants in the landscape.  During the summer we are clued in to water stress by wilting and dropping leaves.  Plants that experience fall and winter drought can’t tell us something is wrong until the next year when they fail to thrive the next year.  Fall and winter drought can lead to root injury or death.  These drought-injured plants may not show symptoms of the problem until the next season or even the next year.  In fact they may leaf out and flower just fine in the spring, relying on stored food reserves.  Once that energy supply runs out plants weaken and start dying back.  Even if a plant isn’t killed outright, it is made more susceptible to insect and disease attack.

This type of “winter” injury seems to be more common than we realize in this area.  For the past several years, we have been losing many of our area birches.  This has been attributed to past winter droughts and cold temperatures without the benefit of insulating snow cover.  Birches are particularly sensitive to fall and winter drought.  Weakened by this, the birch trees that weren’t killed outright have become increasingly susceptible to attack by the bronze birch borer, which attacks and eventually kills weakened birch trees. 

Other shade trees are also susceptible to winter drought damage, especially those with shallow root systems.  This includes Norway maple, silver maple, linden, Colorado blue spruce, Norway spruce, and many other evergreens.  Shrubs are also vulnerable to winter drought damage, especially those growing up close to the house or in a warmer location.  This includes junipers, Oregon grape-holly, and euonymus.

So what’s the answer?  It’s simple.... water the landscape in the plants and the fall.  Yes, it will be work and you’ll have to use your domestic water but, the effort will be worth it when you see that your plants survive and others around you don’t do as well as yours.  I’m not talking about watering plants every day.  .... you’ll probably only have to water a couple of times in the fall to prevent damage. 

The most critical time to water is in the fall just before cold weather hits or during extended warm weather.  It’s interesting to note that not so many years ago, horticulturists thought it was a good practice to insure dormancy by drought stressing plants in the fall and this decreased the chance of winter injury.  Research since then has indicated that the reverse is true... so now we try to insure plants aren’t drought stressed in the fall.  The soil should be kept slightly moist down to a depth of 18 inches for most shrugs and a depth of 18 to 24 inches for trees.  Water only when the air temperature is above freezing and the soil isn’t frozen... which isn’t usually much of a problem during the fall but can be during winter dry spells.  Water early in the day to allow water time to drain away from the bases of plants.  (Frozen water next to the bark can physically damage trees and shrubs.)  Soaker hoses work well for applying the water slowly and where needed.

Since fall and winter watering will be more labor intensive for you, apply the water where it counts the most... in the root zone.  Consider that established trees have roots that go out at least as far as the tree is tall and usually further.  It is in the “dripline” and just beyond where most of the water should be applied.  The “dripline” is an imaginary vertical line that is perpendicular to the longest side branches of the tree and perpendicular to the ground.  Water applied at the tree trunk base is wasted because there are no water absorbing roots there.

Watering recently planted trees and shrubs is a different story.  Their roots don’t go out that far yet.  In this case you will want to water the root ball zone and just beyond.  The aim is to water where the roots are.  This makes sense doesn’t it?

Keep in mind that even if we do get lots of rain during the fall, shrubs and trees close to the house foundation or located under eaves may still need watering.  Located in these areas, they receive little precipitation and they lose more moisture than other plants because of their proximity to the structure and reflected heat from the walls.

New Pesticide for Control of Shade Tree Insects

New Pesticide for Control of Shade Tree Insects

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

There continues to be concern about our dependency on chemicals for pest management in yards, gardens, and agricultural crops.  Chemicals that we have relied upon for years have recently come under scrutiny for one reason or another.  Many of these "old" chemicals have one or more objectionable characteristics, such as they're very hazardous to the applicator due to their extreme toxicity in a concentrated form, they don't break down very quickly in the environment, they pose a threat to groundwater due to their leachability, or they may lead to long term health effects like cancer.

It's been said that, "Necessity if the mother of invention."  This is true when it comes to pesticide chemistry.  With concerns about old pesticides and their chemistry, the pesticide industry has worked hard at formulating new and safer chemicals which will be more environmentally friendly and thereby more acceptable to consumers.  Of course, these new chemicals must also do a good job of controlling the pest... whether it's a weed, insect, or plant disease.

One fairly new chemical on the commercial market is an insecticide known by the trade name of Merit.  Its common chemical name is imidacloprid.  Merit has been quite popular for several years in areas where lawn grubs are a problem.  However, since lawn grubs are not usually a serious problem in this area, you've probably never heard of Merit.  Merit is also labeled for use on trees and shrubs. Local pest control operators have started applying Merit to area landscape trees with fairly good results.

Let's take a look at this new chemical.  Bayer Corporation, who manufactures Merit, indicates that it's a "broad-spectrum insecticide."  This means that it kills a variety of different insects.  The label lists numerous sucking insects and some chewing insects which can be controlled with Merit.  These include aphids, adelgids, elm leaf beetles, lacebugs, leafminers, leafhoppers, pine tip moth larvae, scale insects, and thrips.

Bayer also indicates that Merit is a systemic insecticide which means that it's taken up into the plant sap and moves to different parts of the plant.  Bayer indicates that it can be applied as a foliar spray to the leaves or applied to the soil for root uptake.  They point out that soil application is more efficient and effective for long-term insect control.  

Merit uses "new chemistry" and is very low in toxicity to humans, mammals, birds, and fish.  It's used at extremely low rates and there's no odor or phytotoxicity problems (damage to plants.)  Soil treatment also eliminates the chance of spray drift, reducing the potential exposure of humans and pets to this chemical.  Most beneficial insects are also safe with soil applied Merit.

Merit can be applied to the soil as either a drench or by injection.  Commercial applicators often opt for soil injection because it's the easiest to apply when they have the proper equipment.  Injections can be placed right at the base of the trunk; in a grid pattern below the tree's dripline; or in a circle at the dripline of the tree.  Bayer research indicates that all of these methods of placement are equally effective.  Many commercial pest control applicators choose the base treatment because it's most efficient.  Injections are placed a foot or less away from the base of the tree at a depth of six to twelve inches.  If the soil is dry, it's important to follow the application with adequate irrigation to thoroughly moisten the soil.  The soil in the application area should be kept moist for seven to ten days after treatment.  The number of the recommended injection sites increases with the size of the shrub or tree.

Now here's one of the interesting characteristics of Merit...  it will provide season long control if it's applied in late fall or early spring.  It takes about two to three months after application for it to become fully effective in the control of foliar pests on large trees.  It takes about a month after application on small trees and shrubs to become effective.  With this time lapse between application and full effectiveness, it's obvious that it must be applied prior to the time that the anticipated pests will be at their peak.  Foresight is much better than hindsight when using Merit. Fall application would logically be the best time to treat shade trees for aphid problems. 

Merit is now available to home gardeners so that they can treat their own trees and shrubs.  Merit is living up to it's manufacturer's promises... as long as it's applied early enough to become fully effective... and enough water is available to keep the soil moist for at least a week.  As Merit gains in popularity we'll probably not even miss some of those older chemicals that controlled the same pests, but were not as safe to use or as friendly to the environment.  Necessity made it happen.

Trees and Allergies

Trees and Allergies

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Are gardeners, horticulturists and plant breeders the ones to blame for the rise of urban allergies?  Thomas Ogren seems to think that they are largely responsible.  Hay fever or seasonal allergic rhinitis is a big problem in this country with more than 35 million people being affected by airborne plant pollens and molds.  Chronic rhinitis is one of the leading causes of missed work days in this country. Treatment for this problem costs over 6 billion dollars a year and one out of every six doctor’s office visits are allergy related..  Ogren is pointing the finger of blame at people who love and work with plants.  How could such an innocent passion be the cause of all this?

Ogren is a former nursery owner with a Master of Science in Agriculture from Cal Poly University.  About 15 years ago he changed directions and has become an allergy researcher. Ogren seems to think a big part of increasing allergy problems is due to the increased exposure to air-borne plant pollens.  Allergies develop from repeated exposure to specific allergens, with plant pollens being the most common outdoor allergens. So why might plant enthusiasts be responsible?  It’s because they unwittingly changed the tree and shrub community in cities and towns to a predominantly male dominant population.  Yes, plant enthusiasts have been sexist.

Ogren points out that this sexist discrimination began back in 1949 when the USDA Yearbook “Trees”  recommended selecting male trees that didn’t produce litter or seeds.  Since then plant people have encouraged planting male trees and shrubs because of the less mess, lower maintenance characteristics they offer. 

At the time UDSA “Trees” yearbook was published, about fifty per cent of the trees in our cities and towns were female.  Since that time there has been a shift to mostly male, pollen producing trees. Also in the 50's, American elms were the predominant street tree across much of the nation. The elms which are monecious have both female and male flowers on the same tree and are generally insect pollinated.  Because they’re not wind pollinated, the elms caused limited allergy problems for city dwellers. 

Along came a disease, called Dutch Elm Disease, that destroyed the population of elms in most American cities.  That left many cities without trees along their streets.  Knowing the value of trees, urban and rural communities replaced the stately elms with other types of trees.  Regrettably these replacements have turned out to be predominantly male, pollen-producing, wind pollinated species.  Are you starting to see the problem? 

To make things a little clearer let’s talk about sex and pollination.  Some trees are “monecious”, having separate male and female flowers on the same plant. Examples include honey locust,  oak, sweetgum, pine, spruce, and birch. Other trees and shrubs are “dioecious” having female and male flowers on separate plants.   Examples include ash, willow, cedar, juniper, cottonwood, mulberry, box elder, holly, yew, and smoke tree. Yet another type are “perfectly flowered” with flowers being both female and male. Examples include dogwood, crabapple, cherry, redbud, magnolia, flowering pear, plum, and hawthorn. 

From an allergy perspective, perfectly flowered plants don’t cause as many problems.  Their pollen tends to be heavy and sticky.  Pollen is usually transferred from the male to the female parts of the plant by insects.  The dioecious and monecious plants are more likely to cause allergy problems because most are wind pollinated.  For wind pollination to be successful they must produce lots more pollen.  From the pollen standpoint, Ogren feels that dioecious males are worst plants because they only bear pollen and dioecious females are the best because the don’t produce any pollen.

Let’s consider that two-thirds of the pollen from wind pollinated trees and shrubs is distributed within 60 feet of the source and 90 per cent of the pollen within 90 feet. Grasses and herbaceous plant pollen tends to travel only a few yards from the plant.  That means that for most of us the pollen that aggravates our allergies is in the landscape at home, school, or work. That means we can have partial control over the situation by selecting and planting trees, shrubs, and flowers that won’t cause as many allergy problems caused by plant pollens. 

Some communities have already come to the realization that certain pollen producing plants are causing a problem.  Tempe, Arizona and Las Vegas, Nevada have outlawed the planting of olive and mulberry trees because of they’re extremely allergenic.  Las Vegas already has 200,000 male mulberry trees.  These male trees were no doubt planted to avoid the female trees and their very messy fruit. Other communities are banning the planting of Bermuda grass lawns because of the large amounts of pollen they produce. Albuquerque, New Mexico has banned the planting of many male plants trees and shrubs and has ordered the labeling of allergenic plants in nurseries and garden centers.  We will no doubt see more regulations and planting ordinances enacted in the future. 

I’m not sure we need laws and ordinances, as much as we need awareness and encouragement to plant trees, shrubs and flowers that won’t cause as many allergy problems.  However, we need to know which are the “good” plants and which are the “bad” plants.  Ogren developed a trademarked scale called OPALS(TM) or the Ogren Plant Allergy Scale.  With this scale plants are ranked from 1 to 10, with 10 having the greatest potential to cause allergy problems.  Various criteria involving 70 factors are used to rank plants.  The scale has been reviewed by allergists and botanists and judged to be a useful tool. USDA researchers at the Northeastern Research Station in Syracuse, New York have started using OPALS(TM) for its allergy projections in major U.S. urban areas.

How can we possibly use the scale to protect ourselves from allergy attacks?  The answer is to start planting landscape with plants that are on the low end of the OPALS (TM), five or less.  However, this is a major shift in thinking for gardeners, nurserymen, plant breeders, and municipalities. It will take time to create awareness and acceptance. We’ll need to have more tolerance for litter and some “messiness”, but a little extra work may well be worth it to save us from runny noses, watering eyes, and other allergy miseries.

To learn more about OPALS (TM) you might want to pick up Thomas Ogren’s book, Allergy Free Gardening published by Ten Speed Press.  In the book Ogren discusses his theories about the increase of allergies and asthma in this country and he lists thousands of plants with their OPALS (TM) rating.  If you’re an allergy sufferer, you may want to use it as a guide when shopping for garden and landscape plants.

I bet you’re curious about how some plants are ranked on the scale.  Here’s a sample:

Male Ash Trees: 9-10

Female Ash Trees: 1

Male Red Maple: 8-9

Female Red Maple: 1

Male Honeylocust: 7   

Female Honeylocust: 1

Male Junipers: 10       

Female Junipers: 1

Dogwoo d: 5


Flowering Pear: 4


Flowering Plum: 3


Flowering Cherry: 7


Double-flowered Flowering Cherry: 1


Birch: 7


Red Oak: 8


Pine: 4


Spruce: 3



Trunk Cracks and Wood Rot

Trunk Cracks and Wood Rot

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

Have you ever seen cracks in tree trunks?  Radial separations of bark and wood are usually referred to as frost cracks.  Almost every reference you’ll look at on tree care blame frost cracks on extremes fluctuations of temperature in the winter.  In fact, most sources blame frost cracks on the phenomenon of “southwest winter injury.”  This type of injury is attributed to the bark and wood of trees warming up on the southwest side on a sunny but cold winter day.  The tissue deacclimates, coming out of its complete winter dormancy.  When the sun goes down and the temperature drops rapidly, the tissues can’t reacclimate quickly enough and the water in the tissue freezes, causing cell damage.  The theory has been that sometimes this tissue damage can result in wood and bark cracks.

For many years bark cracks and trunk splits were attributed only to frost.  It wasn’t until the last twenty years, under the guidance of former U.S. Forestry Service scientist and author, Dr. Alex Shigo, that researchers have realized the real cause of split trunks and bark cracks.  Apparently “frost” cracks start from a wound that may have happened much earlier in the tree’s life.  These wounds are believed to be formed at the death of a root or branch.  This wound can create an internal “crack” that develops as a result of stresses from drying, wind, or temperature extremes.  When other pressures occur, such as the thawing and freezing that occurs in the “southwest winter injury” scenario, the internal cracks develop outward.

While the frost leads to a visible crack and open wound, it’s not the real cause of “frost cracks.”  The real cause of the cracks are the death of major roots at planting time; physical injury to roots from construction or soil compaction; wounds created by flush cut pruning; dead limbs resulting from topping cuts, physical injury to the tree trunk, and poor graft unions.

What is the problem with cracks in the tree wood?  Even though callus forms at the edge of the crack and may appear to close it, the wood will never re-knit together.  It’s not like broken bones on humans.  Once those wood fibers are split, they are split forever.  This weakens the mechanical support of the trunk or limbs involved. 

Which came first the chicken or the egg?  It was thought that trunk cracks developed first and then the decay developed in the center due to the opening created by the cracks.  Shigo discovered that the decay is there before the crack, coming from the dead roots, branches, or wounds which instigated the crack.  Additional fungi and insects may attack the tree as a result of the outward crack, but decay organisms are already present before the outward crack develops.

What can be done about split trunks?  Not much really.  One must realize that most of the wood cells of a tree are dead cells.  As I mentioned, they will not “knit” or grow back together.  In the case of most trunk cracks, the internal wood of the tree is already subject to wood decay from fungi.  The tree may function quite well with little effect from the crack or internal decay, since    the vital functions are carried out in the outer few inches of the tree's circumference.  The real concern is for the tree’s structural integrity.  If wood decay becomes substantial, the tree will become a hazard.

Don’t try to paint or seal the split with any type of compound.  They don’t help and they can aggravate the wound.  The best you can do is clean or smooth the edges of the wound with a sharp knife.  Start at one end of the split, smooth around one side of the wound, going no more than one‑half to one inch back from the split bark.  Stop at the other end and do the same procedure on the opposite side of the split.  This aids in callus development.  Sterilize the knife between cuts by dipping for several minutes in a 1:10, bleach:water solution or a 70 percent alcohol solution.

Occasionally “bleeding” or slimy seepage occurs from cracks and wounds.  This is called wetwood or slimeflux.  It is caused by an infection of the wood by a bacterium.  This bacterium feeds on the sugar in the wood and produces a foul-smelling gas and liquid basically through a fermentation process.  The infection can kill some of the bark cambium and can stunt growth but, usually doesn’t kill the tree.

Not all “cracks” are serious cracks that form in the wood.  Some cracks are simply bark splits and are not likely to be fatal to trees, although they will, in some cases, allow entry of disease organisms which can lead to wood decay.  Most of these bark splits are fairly superficial, forming mainly in the outer bark.  Splits occur vertically along the trunk or main branches.  In many cases, bark splits will often close or callus over completely leaving only a slight ridge in the trunk.

Causes of these splits include various environmental factors, such as rapid growth spurts, drought, fluctuating conditions of excessive and deficient, temperature extremes, southwest winter injury, late fall growth, and sun scald.  Trees that are most susceptible to this type of injury are those with thin bark, such as Kwanzan cherry, maple, and certain fruit trees.  Young trees also seem more prone to bark‑splitting than older, established trees.

So the next time you see a bark split or a crack in the trunk of a tree be aware that the real cause of the problem is not frost.  They are reminders that tree care from the time of planting to pruning all contributes to a tree’s health, now and in the future.

Aphids Make Trees Sticky

Aphids Make Trees Sticky

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

 “Why are the leaves of my trees shiny and sticky?  My trees are weeping and get everything underneath so sticky, what’s wrong with them?”  As summer progresses, we’re starting to see more insect pest problems bothering trees, shrubs, and other ornamental plants.  One major insect offender is aphids.  Aphids are often a perennial problem on some types of plants.  With trees and shrubs, like maples, ash trees, and roses, it’s a continual battle to keep aphids at reasonable levels.

Knowledge of your adversary can give you a tactical advantage in your yard and garden confrontations.  Aphids are soft-bodied insects which feed on plants by piercing leaves, stems, or twigs and then sucking out plant sap.  They often suck out more sap than they can use and secrete the excess as a sticky waste... called “honeydew.”  Honeydew is mostly sugar and water and isn’t harmful.  This sticky goo, or honeydew, may be eaten by other insects, or a black mold may grow on it.  This black mold, called sooty mold, is not harmful to the plants.

Along with the problem of “sticky trees,” aphid feeding can cause other problems.  Excessive feeding can lead to a loss of plant vigor and retard growth.  Aphids also secrete a saliva into plants while they feed.  In many plants this saliva causes distorted plant growth in the form of curled leaves, swollen nodes, and distorted growth.  Repeated severe annual infestations can lead to plant die-back.

Before trying to manage any insect population that has gone beyond tolerable levels, you need to understand the insect and it’s life cycle.  There are many different types of aphids with varying life cycles.  Entomologists say that there is probably at least one species of aphid that feeds on nearly every type of plant... trees, shrubs, flowers, vegetables, row crops, and weeds!  With so many different species of aphids it’s hard to know the exact life cycles of all of them, especially since aphids seem to have such a complex and strange life cycle.

Aphids can overwinter as eggs or mature adults.  In the spring, the eggs hatch into “Big Mommas” (actually, entomologists call them “stem mothers”) who produce live young without the “disadvantage” of mating.  These daughters also mate asexually, producing even more daughters.  You can see that without the need for mating that aphid populations can build up quite rapidly.  In fact, it has been estimated that one cabbage aphid “Momma” can be responsible for a family of 1,560,000,000,000,000,000,000,000,000 aphids by the end of the season... under ideal conditions. 

If you’re wondering where all these aphids might be hanging around, they’re probably not all still alive.  Aphids take about one week to mature and then most live for only about three weeks.  Many become the dinner for other insects.  If the colony becomes too crowded or the host plant is stressed, winged aphids are produced so they can move out on their own and seek new sources of food. In the fall, some aphid species produce both male and female aphids for the purpose of mating.  After mating the females lay eggs in protected locations, such as in buds or cracks in the tree bark, for overwintering.

Now we know the life cycle, but what about how aphids look?  Identifying the right pest is important.  As mentioned before, aphids are soft-bodied insects.  They come in a variety of colors including green, white, yellow, brown, black, gray, pink, purple, or red.  Some are even covered with a whitish “wooly” or cottony coating.  Aphids are usually found in large groups on plants, often on tender new foliage or the under sides of leaves.  Most aphids don’t move too fast... as you can’t budge them easily once they’ve found a good source of food.  They know a good thing when they taste it!

Now that we know more about how aphids live and grow, let’s talk about when and how to “control” them.  There are some fairly innocuous methods you can try... when and where they’re practical.

  1. First look for signs of natural control.  Aphids have a number of natural enemies... ladybird beetles and their larvae, green lacewings, small parasitic wasps, syrphid fly larvae, predacious stink bugs, and assassin bugs.  If you’re able to find evidence that these natural enemies are present and working, don’t do anything unless the aphid population appears to be beyond their control.
  2. Dislodge aphids with a fine but forceful spray of water from your hose. Be sure to move the spray back and forth as well as directing it towards the undersides of the leaves.  This will kill some aphids and many will not make it back to the plant.  Repeat this every several days.  This method of control can’t be used effectively on small or tender plants.
  3. On some plants you can simply wipe aphids off plant stems or buds.  However, you may want to wear a pair of garden gloves to do this.  Snip off badly infested branch or stem tips.  Avoid fertilizing your plants with too much nitrogen.  Soft, lush growth encouraged by excess nitrogen is exactly the type of growth that aphids thrive upon.
  4. Avoid aphid buildup early in the season on woody trees and shrubs by applying dormant oils to plants that have had problems with aphids in the past.  The dormant oil should be applied in early spring when temperatures are above freezing, but before the buds start to show green tissue.  Use according to label directions... of course.
  5. If aphids are out of control and an insecticide is warranted, first consider the use of insecticidal soaps.  These are good materials to use because they protect a number of the “good” insects and they are very low in toxicity.  It’s important to get good coverage and to spray both the tops and bottoms of the leaves.  Repeat as needed.  Check product labels to avoid applying to plants sensitive to soaps. Don’t apply to stressed plants.
  6. When aphid infestations are so severe that no other method of control is practical, a chemical insecticide may be needed to prevent further plant injury.  There are a number of pesticides labeled for control of aphids on plants.  However, some of these can only be used on ornamental plants because of their systemic action... meaning that they’re absorbed into the plant sap and move within the plant’s vascular system.  Systemics are particularly useful when aphids are protected by the leaves curled with their feeding damage.  Curled leaves protect aphids against contact insecticides.  Some materials are systemic sprays, such as Orthene, which is taken up into the plant sap of treated leaves.  Others, such as Merit or Di-Syston, are applied to the soil and absorbed with water by the roots.  

Root applied systemics are a practical way of treating a large shade tree with severe aphids populations.  They’re also less detrimental to the beneficial insects in the area.  Di-Syston and Merit (imidacloprid) are available to home gardeners.  Other soil applied systemics, such as Cygon, are available only to licenced commercial pest control operators.  Cygon can be used by home gardeners as a spray, but it’s illegal for them to use it as a soil applied drench on shade trees.  Keep in mind that most systemic insecticides are quite toxic to humans and animals.  Some plants may also be injured by the use of certain systemic insecticides.  Carefully read and follow all the label directions when using a systemic insecticide or any other pesticide product.

Aphids can be pesky, but a little knowledge about how they behave and how to safely manage their populations can lead to truce in your yard and garden.

Lawnmower Blight

Lawnmower Blight

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Watch out for "mower and line trimmer blight" damage to your trees.  This dastardly disease is the result of tissue damage to the trunks of trees from careless mowing techniques and overenthusiastic weed whacking.  The bark of young trees is especially vulnerable to attack because its thin and tender, but older trees with thin, smooth bark are also susceptible.

Lawnmower blight damages the cambium tissue layer that lies right underneath the bark.  It's only a few cells thick.  The cambium is important because it produces the cells, which develop into the conductive tissue in the trunk.  Damage to the cambium results in decreased flow of water and nutrients upward and sugars downward in a tree.  A tree is "girdled" if damage occurs to the tree all the way around the trunk.  Eventual death is the result of girdling.

Too often we carefully plant and tend our trees, but fail to protect them from "lawnmower blight."  Once a tree experiences this type of damage to its trunk, there isn't much you can do.  Cambium tissue cannot be replaced... it doesn’t regenerate and the tree can't heal itself.  The best control is prevention!

The very best way to prevent damage to the trees is to eliminate grass and weeds growing close to the trunk.  Create at least a 12-inch “weed-free-zone” around the trunk of the tree.  This eliminates the need to mow and potentially damage the tree.  (If you use glyphosate or Roundup to eliminate weeds around the trunk of your tree, be sure to keep the chemical off the bark.  Young bark can absorb the chemical and result in damage.)  Edge the “weed-free-zone” with vinyl edging, bricks, or cedar bender board.  Mulch the area with bark or compost.

Keeping the “zone” weed and grass free isn't just aesthetically pleasing; it's also good for your tree. Research has shown that allowing grass to grow over a young tree's root zone will stunt the tree's growth.  This happens because the grass is a good competitor for water and nutrients.  Another reason is that grass exudes chemicals that retard root growth. 

If maintaining a “zone” around the trunk of your trees just isn't going to work, you can cage your trees with wire fencing or heavy plastic netting that is about 12 inches high.  However, you should have at least a three-inch, weed-free-zone right at the trunk base and keep the caging material from direct contact with the trunk.  This three-inch zone is important because otherwise the grass and weeds will grow up inside the cage resulting in an overgrown, unkempt mess.

Some folks use 6-to12-inch long pieces of large, plastic irrigation pipe to protect the trunk of their trees.  They slit the pipe on one side and then they pry it open to slip it over the trunk.  While this might not be the most attractive way to protect the tree, it does the trick of preventing mower blight.

Why Are All the Birches Dying?

Why Are All the Birches Dying?

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Even if you don’t own a birch tree, it would be hard to ignore the fact that so many birches in our area are dying.  There are various factors involved, but the causes involve stress, winter injury, and a devastating insect borer.

Birch trees are generally not well adapted to our region.  They’re better adapted to areas where the summers don’t get quite so hot; where the soils are more acid and have more organic matter; and where there is snow over the roots during the cold parts of winter.  In their native habitat you’re most likely to find them at cooler, higher altitude locations growing close to water.

Birch Tree Roots Need Air

Birch trees have a rather large system that can spread twice the distance of the tree’s height or more!  A mature tree’s root system can be as large as one-third the size of a football field.  Obviously, birches need room to grow and shouldn’t be planted in areas that restrict their growth.  Small planting areas or sites close to sidewalks, driveways, and building foundations should be avoided. 

Compacted soils limit air getting to roots.  When planting birches you need a soil that has not been compacted by construction equipment.  Compacted soils should be “ripped” or deeply cultivated before planting birches.  (Keep in mind that you need to loosen the soil in an area about one-third the size of a football field.)  If the soil becomes compacted after planting due to traffic from people, pets, or vehicles or due to the use of impact sprinklers, aeration is a must.  Aeration will help get air to the roots and keep the trees healthier.

Birch Trees Need Water

Remember, in their native habitat you will most likely find birches associated with a water source... rivers, streams or lakes.  Watering a birch tree just with your lawn irrigation is inadequate.  Birch trees need much more water than the leftovers they receive from lawn watering. This means watering the trees once a week during the hot part of summer and once every two to three weeks during the cooler parts of the growing season.  Watering deeply with a soaker hose placed at the dripline (the perimeter of the branches) is what’s needed.  After watering deeply the soil should be moist to a depth of 18 to 24 inches.  Watering should continue until the end of October.  If the winter remains mild and warm, then it’s also recommended to water at least once a month if the soil becomes dry.

While it would be very hard to mulch the entire root system of a mature tree, young birch trees benefit from mulching the root zone with bark chips or compost.  This helps maintain soil moisture and keeps the roots cooler.

Birch Trees Need It Cool

“Coolness” or mild summer temperatures are not something we can control, but we can avoid planting birches in sites where they will be under additional heat stress.  Don’t plant them on south or west facing slopes.  Don’t plant them where they’re surrounded by paving or asphalt.  Don’t mulch them with stone or rock mulches.  Avoid planting birches where they’ll also be exposed to strong, drying winds.  Shelter them from wind and sun on the north sides of buildings or with other trees.

Is It Decline or Is It Borers?

Too many birch trees in our area are declining and dying back because they’ve experienced considerable stress.  This stress and subsequent decline of the birches has been the result of inadequate or improper watering, compacted soils, and damage to the roots from cold winter and hot summer temperatures.

Identifying Bronze Birch Borer

The weakened state of local birches has made them very vulnerable to attack from the bronze birch borer.  This is a wood boring beetle pest that is decimating many local birches.  The first symptom of bronze birch borer attack is the wilting and dying back of the top portion of the tree.  However, this is pretty much the same symptom that results from the general decline of the tree. 

To determine if the bronze birch borer is at fault, an examination of the main branches and trunk at top of the tree needs to be made.  The bark will be bumpy and ridged from the borer larvae feeding beneath the bark.  Slicing into the area right below the bumpy bark will reveal serpentine trails filled with the dark excrement of the feeding larvae.  Once the feeding larvae mature they pupate and turn into adult beetles.  The adults exit the tree leaving characteristic D-shaped holes in the bark. These holes are sure signs of bronze birch borer activity.

Resistant Varieties

What can be done to control bronze birch borer in our birches?  Well, the very first thing is to plant trees that are more resistant to attack from the borer.  Unfortunately most of the types of birches planted in our area are very susceptible to bronze birch borer attack.  This includes the European white birch (Betula pendula,) Jacquemonti Birch (Betula jacquemontii,) and Young’s weeping birch (Betula pendula ‘Youngii’.)  The River birch (Betula nigra) and the Heritage birch (Betula nigra ‘Heritage’) are probably the most resistant birches available.  Unfortunately, the River birch and Heritage birch don’t have the much-desired white bark.  Instead they have an attractive peeling apricot colored bark. 

The Whitespire senior birch (Betula platyphylla japonica `Whitespire Senior’ is moderately resistant and does have white bark.  However, it’s important to get `Whitespire Senior’ that has been propagated from the original, superior tree in Wisconsin.  Other trees that are simply designated as “Whitespire” may be seedling trees that are probably not resistant to the borer.

Managing Bronze Birch Borer

If you chose to plant a tree that isn’t resistant to bronze birch borer, your next line of defense is to keep the tree as healthy as possible and growing vigorously.  Plant the tree in a suitable location where the soil can be kept cool and moist.  The north or east side of your home is best.  Be sure to water deeply during the growing season, especially during the hot part of summer.  Mulch the roots with shredded bark, wood chips or coarse compost.  Don’t use rock mulches!

Fertilize the tree to maintain vigorous growth if needed.  Use a slow-release tree fertilizer and be careful not to over-fertilize.  Don’t prune birch trees unless there is a very good reason to prune.  When you prune, avoid pruning in late winter or early spring because the sap will bleed.  Absolutely do not prune until July during the growing season because adult female bronze birch borers are attracted to trees with fresh pruning wounds. 

Chemical control of bronze birch borer is difficult.  Pesticide applications are best applied to the bark to prevent reinfestation by adult borers that have already emerged.  By the time a borer attack is evident, chemical pesticides will have limited or no effect on borers feeding under the bark.  To prevent reinfestation the recommended sprays are applied to the bark and the leaves.  These should be applied in late spring and early summer (May through June.) They must be applied with thorough coverage to the bark because the adults lay their eggs under loose bark and inside bark cavities.  Timing is critical to get the adult beetles and the baby larvae before they eat their way back under the bark where they’ll spend the rest of the summer feeding.  In the fall they pupate or transform into a resting stage just underneath the bark for the winter.  In the spring they mature and transform into adults and then emerge... leaving D-shaped holes.

Systemic insecticides applied to the soil for uptake by the roots or injected into the tree usually have no or only limited effectiveness on the borer larvae in the tree.  The systemic insecticides which do provide some control are only effective when the larvae are actively feeding in the summer and early fall.  Spring and fall applications of these systemics is not practical.

If a birch tree has been infested by bronze birch borer, it’s also important to prune out infested wood as soon as possible.  Pruning cuts should be made properly well below the infested area.  Infested wood should be destroyed or disposed of as soon as possible.

Hot Weather and Leaf Scorch on Trees

Hot Weather and Leaf Scorch on Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It takes longer for trees and shrubs to show signs of distress from lack of water or improper watering practices than other smaller plants in vegetable and flower gardens..  Leaf scorch is a possible sign of water stress.  Mild leaf scorch appears as the yellowing and then browning and drying of the tips and margins of leaves.  More severe scorch appears as the yellowing and then browning of tissues between the main veins of the leaf or large angular blotches of brown tissues between the veins. (In many cases no yellowing occurs at all, tissues just turn brown.) Extremely severe scorch involves the browning and death of entire leaves.

Leaf scorch is a physiological problem related to watering.  The leaves are telling us that they’re losing water at a faster rate than can be replaced by the plant.  Leaf tissues that are furthest from the veins (the margins and areas between the veins) are the first ones affected by the lack of water. Environmental conditions that increase the water demands on a plant tend to increase the severity of leaf scorch.  Hot temperatures, low humidity, high light intensity, and wind all increase the rate of water loss from the leaves.

Sometimes leaf scorch is simply due to a lack of adequate irrigation during the demanding summer weather.  However, anything that interferes with the uptake and transport of water to the leaves can lead to leaf scorch.  Compacted soils; girdling, choking, or underdeveloped root systems; root damage from excavation; and trunk injury from mowers and weed trimmers are often involved. Certain disease and insect problems may also be part of the problem.   Recently transplanted trees with unestablished root systems are frequent victims of leaf scorch.  

Some types of trees and shrubs, such as Japanese maple and flowering dogwood, are not well adapted to hot summers in an arid climate like ours.  To survive and thrive in our region, they do best where they’re protected from excessive heat, afternoon sun, and drying winds.  In more exposed locations or surrounded by reflected heat from buildings and pavement, they will often develop leaf scorch.  They also benefit by having their roots kept cool with a layer of bark mulch. 

Strangely enough, leaf scorch can also be caused by too much water. Saturated soils don’t allow roots to get the air that they need.  Suffocated roots die and the plant can’t take up water... creating the same symptoms that appear if there isn’t enough water.  Saturated soils can lead to fungal and bacterial root rots and eventual death.

If leaf scorch develops on a tree or shrub of yours, try to determine the cause.  Don’t simply start dumping more water on it, assuming that too little water is the problem.  Check the roots and trunks for problems.  Consider all the possible factors that might be involved, but don’t forget to check soil moisture too.

It’s easy at this time of year to be derelict in your watering duties. Contrary to the belief of many, most trees don’t have tap roots and aren’t able to make use of the water in the water table. Most tree and shrub roots that absorb water are located in the top 18 to 24 inches of soil.   Trees growing in our region depend upon us and irrigation water to supply their moisture needs.

During the hot part of summer, trees and large shrubs should be watered with “deep” watering about once a week.  More shallow lawn watering is inadequate to supply their needs. Use a soaker hose to provide this deep watering.  Soaker hoses are made of porous canvas, plastic, or rubber. They allow water to seep out slowly and are useful in watering trees, flowers, vegetables, and shrub beds. Don’tprovide the water at the base of tree trunks where it’s wasted.  Apply water to the area known as the “drip line”, the outer edge of the branch spread.

Special attention should be given to trees and shrubs planted within the last two years.  Make sure they’re getting enough moisture by checking their root balls.  They can’t “tap” into surrounding soil moisture until their roots grow out of the original root ball. It’s important to keep their root zone moist... but not wet.

How much water does a tree need to keep it “happy”. Research has shown that a mature silver maple can lose over 000 gallons of water a day through its leaves, and a mature oak tree can lose over 400 gallons a day.  However, rather than worrying about how many gallons of water to give your tree, you should be checking the soil moisture in the root zone.  Use a spade, shovel, or probe to see if the soil is moist in the top two feet of soil. 

Prevent hot weather stress in your yard and garden by watering the right way!


Watering Trees

Watering Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Proper watering is always important, but it becomes crucial when the temperature hits triple digits and stays there.  If plants are only provided with shallow waterings every day, they’re probably only getting a fraction of what they need.  Let’s look at the water needs of trees.  Large amounts of water evaporate through tree leaves.  This “pulls” water through the plant.  Water is the “vehicle” that nutrients use to enter the plant.  These nutrients are needed for plant functions and growth.  Water is also needed for vital physiological plant processes.  A lack of water means stress and disruption of plant functions.

While humans are supposed to drink at least eighty ounces of water a day and more in hot weather, trees need gallons of water.  A mature silver maple can lose up to 58 gallons of water per hour on a hot summer day!  This translates to over1000 gallons in a twenty four hour period.  Wow! Watering your tree for 10, 15 or 20 minutes a day just isn’t going to give that big old maple the water that it needs.  It’s like getting only a little glass of water after standing outside all day.

To water trees adequately, water should be applied over a longer period of time that will thoroughly moisten the soil to a depth of 18 inches or more.  Water should be applied slowly enough so that it soaks into the soil without running off down the driveway, sidewalk or street.  An excellent way to apply water slowly is with a soaker hose.  Soaker hoses are made of porous canvas, plastic, or rubber.  They allow water to seep out slowly and are useful in watering trees, flowers, vegetables, and shrub beds.

If you have a solid set irrigation system and numerous trees, soaker hoses might not be practical for you.  You’ll need to work with your system’s timer so that you can apply water for a longer period of time in the same location.  You may want to “pulse” the water, applying it several times with “resting” periods between applications to allow the water to soak in.  Check the soil several hours after you water to make sure that it’s moist to a depth of 18 to 24 inches.

It’s important to point out that the tree roots that absorb water are not right next to the trunk of established trees.  Water applied in the tree trunk area is wasted water.  The fine feeder roots that absorb most of the water for the tree are located at and beyond the “dripline.” The “dripline” is the outer edge of the branch spread.   Newly planted trees are an exception to this rule.  The water absorbing roots of recent transplants will generally be in the area of the root ball.  Care should be taken to keep that root ball moist and water may have to be applied close to the trunk to accomplish this task.

What’s the best time of day to water during the hot weather? It’s probably best to water in the very early morning, but irrigation water isn’t always available when you need it.  If you have a choice, water during the cooler part of the day, morning or evening.  If you water during the hottest times of the day, you lose considerable moisture from evaporation before the plants even get a chance to use it.

It would be a good idea to check out all your sprinkler heads and make sure they’re working properly.  During hot weather, a broken or clogged head might mean a stressed tree, a dead garden plant, or a brown patch of lawn.  If you rely on drip systems to water trees and landscape beds, make sure all the emitters are functioning correctly.

Caution: Even though you want to keep your plants supplied with the water they need, you shouldn’t drown them.  Saturated soils can lead to root rot and the eventual death of trees.

Espalier – Two-Dimensional Pruning for Trees and Shrubs

Espalier – Two-Dimensional Pruning for Trees and Shrubs

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Trees and shrubs are part of our three dimensional world.  It takes an adventuresome gardener to turn a three dimensional plant into one with only two dimensions.  Espalier is the art of pruning that involves controlling tree and shrub growth in a single plane... with the support of a building wall, fence, or trellis.  This type of pruning is an ancient art that dates back to Roman times and was later refined by medieval Europeans to save space in the walled gardens around castles, cathedrals, and monasteries.  They were able to reduce the space needed to grow fruit by keeping the growth relatively flat against garden walls... leaving open space for other garden crops. 

Espaliering also proved useful in cooler climates with shorter growing seasons.  By espaliering fruit trees against south and west facing walls, early gardeners found that they could take advantage of the extra heat in these situations, producing fruit in areas where their climate was usually a little too short or too cool to produce fruit.  These south and west facing sites warmed up earlier in the spring and stayed warmer later in the season.

Another advantage to using espalier techniques with fruit trees was the effect espaliering had on the trees.  Espaliered fruit trees usually come into bearing at an earlier age and are generally more productive with deeper fruit color.  This is because of branch angles and the increased light penetration to leaf surfaces that result from the single plane.

The technique of espalier pruning is practiced by some commercial orchardists today because of the early bearing and productiveness of espaliered trees.  Home gardeners and landscapers often practice espalier pruning for its decorative potential.  Using espalier techniques, gardeners can create screens that don’t take up much room and have a softer look than fences or brick walls.  Espaliered plants can also provide decoration for large, monotonous windowless building walls.

Gardeners should take note that espaliering is a technique that takes time and some expense.  You must select the right type of plants and the right site along with making sure you have adequate support for the plant.  Espaliering a tree or shrub involves pruning and training over time to develop and maintain the framework.

Let’s first chat about what types of plants lend themselves well to the art of espalier. Typically you want plants that have long, flexible branches.  Plants with short or stiff branches are hard to train.  You should also consider the mature height of the tree or shrub.  A tree or shrub, whose mature height is much greater than the wall, fence, or structure you plan to train it too, will be unsuitable.  Favored shrubs for espalier include cotoneaster, forsythia, holly, Pfitzer juniper, Kousa dogwood, pyracantha, winged euonymus, flowering quince, star magnolia, and viburnum. Favored trees for espalier include apple, crabapple, and pear.  Fruit trees that bear their fruit on long-lived spurs are the easiest to espalier.  Fruit varieties that have predominantly spur-type growth, such as Red Delicious, Golden Delicious, and Braeburn apple cultivars along with Bartlett pears, work the best.

In selecting a plant, pick a young, vigorous tree or shrub that has a few well-balanced limbs off the main trunk.  Wait until after the plant becomes well established before you perform the extensive pruning needed to start your espalier framework.  In some nurseries you might be able to find plants that already have some initial espalier training. This will make getting started easier.

When planting your tree, be sure to plant it properly to help insure a tree with a healthy root system.  If you’re planting your tree or shrub against a solid wall, the plant should be situated about six to ten inches away from the wall to allow for air circulation behind the plant.

You will need to provide a sturdy support on which to develop your plant’s framework.  This can be done by stringing heavy wire of at least 12 to15 gauge from eye bolts on the fence or wall.  You can also develop your espalier on a free standing trellis.  Just be sure that the trellis is sturdy enough to support the weight of both branches and potential fruit.  When making a trellis for fruit trees, use 4x4 pressure treated posts, sinking the posts two feet into the soil.  Set the posts about ten feet apart, securing the end posts with stakes and guy wires.  With fruit trees you’ll probably want two to three levels of wire with the bottom wire situated about 18 inches from the ground. 

Designing your espalier is the fun part. A well designed and trained espalier is a real work of art.  If you’re doing your first espalier, you should probably start with a simple design. Some of the most common designs are fan-shaped, T-shaped, palmate, pinnate, chevron or V-shaped.  More difficult designs are cordon, basket weave, and candelabra.  Check pruning books in your local library for diagrams of these designs.  With many of these designs, you’ll need to pattern your wire supports accordingly.  If you want something less formal, an asymmetrical informal espalier can be created by allowing the plant to grow and dictate the design.  Training in this case only consists of keeping growth in one plane.

After your tree or shrub is planted and you have its supports in place, you’ll begin its training.  Spread the main branches onto the supports and tie them in place. You need to be careful not to crack or break branches when you bend them into the wanted position.  New growth early in the summer will be more flexible than older branches.

When tying down the branches, use soft string, strips of rags, rubber grafting bands, plant ties, or raffia.  Avoid using wire that can cut into the bark.  Tie the branches to the supports loosely, leaving some extra room for the branch to grow.  Check the ties every three or four months to be sure they aren’t restricting or damaging the branches.  Replace the tie if its hampering growth. 

Branches that aren’t part of the design should be pruned off the spring after planting. Shape the plant every month or so, removing branches or twigs that aren’t in the correct plane of growth.  Training of simple designs may take only two or three years to develop, but more intricate designs will take longer to achieve.

Espalier is a fun way to relieve the monotony of a blank wall or fence. Anyone who has the heart and patience of a gardener as well as the soul of an artist should give it a try. If you’re successful, you’ll have an interesting and attractive landscape accent... if not, you’ll have a really strange and ugly landscape blemish. 

Garden Note: In our region, gardeners should avoid espaliering on south and west facing walls.  Our intense summer sun and heat will be more than most types of plants can endure, plus plants in these types of exposure are more prone to winter injury. Northern exposures may not provide adequate light for flowering and fruiting trees and shrubs. East facing walls are probably the best bet.