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.

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.


Do Black Walnuts Poison Other Plants?

Do Black Walnuts Poison Other Plants?

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

Black walnut leaves, husks, and bark have been rumored to be toxic and not good for use in gardens and compost piles.  The start of this rumor comes from the phenomenon of certain types of plants wilting and dying when growing in close proximity to black walnut trees.  This is called “black walnut toxicity” or “walnut wilt.’ This phenomenon is not new.  In fact, it was noted by Pliny in Roman times.

Scientists have determined that there is a plant chemical called juglone that causes black walnut toxicity.  The largest concentration of juglone can be found in the buds, hulls, and roots of black walnut trees, but it’s also found in the leaves, bark and stem tissue.

Juglone is toxic to many other plants.  Black walnut toxicity primarily occurs when the tree’s roots exude juglone.  Juglone sensitive plants with roots in close proximity to the black walnut roots are affected.  Scientifically, juglone inhibits respiration, denying plants the energy they need for plant growth and metabolism.  Plant responses range from sudden wilt and death to stunted growth.  There are other members of the walnut family, such as Persian walnut, butternut, pecan and hickory, which also contain juglone, but don’t seem to produce it in sufficient quantities to produce toxicity symptoms.

There are a good number of black walnuts grown in this region.  Some area gardeners have been concerned about using the leaves and hulls in their compost because of the rumored toxicity.  According to an Ohio State University Extension factsheet “walnut leaves can be composted because the toxin breaks down when exposed to air, water and bacteria.  The toxic effect can be degraded in two to four weeks.  In soil, breakdown may take up to two months.  Black walnut leaves may be composted separately, and the finished compost tested for toxicity by planting tomato seedlings in it.” 

However, fresh sawdust, shredded leaves, or wood and bark chips from black walnut should not be used for mulching plants sensitive to juglone.  According to the Ohio factsheet, composting the bark for a minimum of six months provides safe mulch even for plants sensitive to juglone.

While rain may leach juglone from leaves and hulls, the juglone is highly reactive and quickly inactivated in the soil.  Juglone is also poorly soluble in water and doesn’t move very far in the soil.

Juglone sensitive plants include apple, asparagus, azalea, birch, blueberry, cabbage, ornamental cherry, chrysanthemum, crabapple, eggplant, lilac, linden, saucer magnolia, narcissus (some,) pear, peony, pepper, petunia, pine, potentilla, rhododendron, tomato, and more.

Ohio reports that problems with black walnuts are not limited to plants.  Horses may be affected by black walnut chips or sawdust when they’re used for bedding material.  Allergic symptoms in both horses and humans may also be produced by close association with walnut trees while their pollen is being shed in the spring.

Stopping Wormy Fruit in Cherries and Apples

Stopping Wormy Fruit in Cherries and Apples

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

There seems to be a great deal of confusion about the need for spraying fruit trees to control insects and diseases.  There are a number of pest problems on fruit trees that require frequent and regular chemical applications to keep the trees healthy and producing quality fruit.  When fruit trees are large, this becomes a difficult, costly, and time-consuming responsibility for their owners.  Smaller, dwarf trees are easier to handle, but still require regular attention.  Owning and caring for fruit trees is not a low maintenance endeavor.

One of the major pest problems faced by backyard fruit growers... the cherry fruit fly.  It’s first and foremost on the list because it’s the pest that causes worms in cherry fruit.  The adult of this pest is the cherry fruit fly.  The adult is a fly that begins to emerge from the ground in late may or early June.  The adult fly takes about seven to ten days to fly around and mate.  After mating, the female lays eggs underneath the developing cherry’s skin.  (No hole is visible in the cherry after she lays the egg.) 

The eggs hatch into small larvae, actually maggots, and begin feeding close to the pit. After about five to eleven days, the maggots each make one or two breathing holes in the skin. (These holes are small but visible.)  Several days after making their breathing holes the maggots are fully mature.  They exit the fruit and drop to the ground where they go into their resting pupae stage.  They spend the rest of the year as pupae in the soil until next spring.

While eating one of these maggots (yuk!) won’t hurt you, it’s certainly not appetizing.  An entire load of commercially grown cherries can be rejected if even one larva is found.  Control of the cherry fruit fly is aimed at killing the adult fly before she lays her eggs under the cherry’s skin.  Once they’re under the skin, pesticide sprays are useless in killing the developing maggot.  That’s why it’s so important to spray regularly and get rid of the flies before they have a chance of laying eggs.

To control cherry fruit fly, backyard cherry growers should recommended sprays regularly, every seven to ten days starting about Mother’s Day weekend..  (Remember, you can’t tell by looking at them whether cherries contain maggots or not.) 

If you’re doing a good job of controlling the cherry fruit fly in your yard but you have a neighbor who isn’t, you may still get maggots in your fruit.  That’s because the flies from your neighbors’ trees are capable of coming over to your tree and laying eggs after you spray.  That’s why it’s important for all backyard orchardists to control this pesky fly... as they cause problems to others growing cherries including the many commercial cherry growers in this area.

Let’s move on to worms in apples.  This is a very different insect pest... the adult is a moth.  Worms in apples are the result of codling moths.  The adult moths emerge sometime in May... about 14 to 21 days after the tree was in full bloom and start laying their eggs on leaves and the surface of developing apples and pears. (They also may attack quince, crab apple, hawthorne, and English walnut.)  It takes anywhere from six to twenty days for the eggs hatch into little larvae.

Once they hatch, the codling moth larvae chew their way into the fruit and proceed to eat their way to the center and eat on the seeds.  As they start to mature, they eat their way out of the fruit, usually exiting at the base.  They then find their way to the branches and trunks to spin a cocoon under loose bark or other little hiding places.  They pupate or go into their resting stage in the cocoon.  There are usually two generations of codling moth a year, but there can be three during longer, warmer seasons.

Control of codling moth is aimed at killing the baby larva before it enters the fruit.  Since it chews on the skin of the fruit before entering, pesticides applied to the fruit will kill the larva both through direct contact and through ingestion.  Because there are at least two generations a year, pesticide applications must be made regularly starting soon after adults start laying eggs and continuing through the summer.  Spray apples and pears on a regular basis with the recommended material starting when codling moths are present and laying eggs.  That’s usually two to three weeks after full bloom... usually around Mother’s Day weekend.

Things you should know about controlling cherry fruit flies and codling moths:

  1. Dormant oil and dormant fungicide sprays do not control either pest.  They control overwintering insects, such as aphids and scale.
  2. Good coverage of the tree with pesticide spray is important. Start at the top of the tree and thoroughly cover the tree just to the point of runoff. Spray the leaves, fruit, limbs, and trunk.
  3. Don’t spray when it’s windy.
  4. Don’t spray when it’s hot... over 85 degrees Fahrenheit.
  5. Avoid wetting the leaves with irrigation sprinklers right after applying the material.