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.