My Apple Trees need Help!

apple tree
Photo credit: EESC slide collection
Q:

I have 5 apple trees and last year the growth was stunted with only 3-4 inches/year and also infested with apple maggots. I don't like the fly traps as one time a small bird was caught, probably following the moth. Is there an organic way, (have been using dormant oil), to get rid of these and also when and how much to fertilize these 4 year old trees?

- Douglas County, Oregon
A:

Let's help you get healthier apple trees. To encourage more growth make sure your soil pH is in a 6-7 range. The natural pH of most of our soils in Douglas County is about 5.5 so adding about 40 lbs of lime per 1000 square ft of soil is a good annual step. That will make nutrients that are present more available. You can also add a little nitrogen fertilizer in March/April. Apply 1 lb of urea to each tree. Spread it around evenly under the drip line of the tree.

Make sure to thin your apples on the trees to just one fruit per spur, and space the fruit at least 6 inches apart. You may need to leave some spurs with no fruit. This will keep the tree from being over burdened by a heavy crop load. A medium load of fruit will allow the tree to put energy into growing more wood. During the first 4-5 years a tree should be making more wood than fruit, so thin a lot of fruit off in spring.

All apple and pear trees will be attacked by codling moth and sometimes apple maggots in this area. It is more likely to have problems with codling moth larvae. To prevent them you will need to spray. It can be an organic spray like Spinosad, Cyd-X or Surround. The use of the traps is to help you time the spray. When the codling moths or apple maggot flies get in the trap that tells you when you need to spray. The traps alone will not control the pests. Dormant oil sprays are good to control over-wintering eggs in trees. Using oil in the summer can help a little but only controls about 20% of the pests.

You can come by the Oregon State University Extension office to visit with the Master Gardeners to discuss raising tree fruit organically.

Steve Renquist
Horticulture Extension Specialist
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