Backyard Apple Tree
we would like to spray for worm prevention on our Apple Tree in our residential back yard. What would you recommend?
Washington County Oregon
Thank you for your question.
Coddling moths and apple maggots, usually perceived as worms, are a perennial problem in apples and pears in Oregon. With a bit of timing and care, you can substantially cut back the incidence of these pests in your home fruit trees.
One thing that is always recommended in orchards is sanitation. Moths and the flies that cause apple maggot are usually pupating (turning into adults) in leaf litter and dropped fruit from last year. Your first line of defense is to rake it all up and destroy the material. Do not compost the material, as home composting does not typically get hot enough to destroy the organisms. You can, if you live in a municipality, load the material in your yard waste bins. That material will be industrially hot-composted and will pose no further pest hazard. If you are in an unincorporated area, you must burn the material on a day proscribed for burning. Call your local fire department for days, safety and conditions.
Next, your trees may be susceptible to pests because they need to be able to derive nutrients from the soils they are in. To do that, the pH of the soil should be between 6 (slightly acidic) and 7 (neutral). This will allow the nutrients present in your soil to become more available to your trees, making them less attractive to pests. Our soils in Washington County tend to be on the acidic to slightly acidic side, this can require yearly amendment with dolomitic or agricultural lime. Test your soil in various areas around the trees with an inexpensive pH test that can be obtained at any good garden center. To raise pH, follow instructions on the bags of lime. Spread it evenly under the drip line of the tree.
You may also wish to thin your fruit to 6" apart after it starts, to make the fruit you have heartier and more resistant to pests. Use traps to determine when to use sprays. When you see coddling moths or mottled winged flies in the traps, you should spray. This will make the organic methods you use more effective. Organic sprays like Spinosad, Cyd-X or Surround can be used when package directions are followed. Also use dormant oils to control overwintering eggs in the trees.
This and other information can be found in Growing Tree Fruits and Nuts in the Home Orchard. It can be downloaded free of charge here: http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/13718/EC%20819.pdf
This publication covers many aspects of tree care and maintenance.
I do hope this information helps. Thank you again for using Ask an Expert.