Worms in my apple trees

Asked February 12, 2020, 4:18 PM EST

What can I do now, in February, to prevent a recurrence of worms in my apple trees?

Jackson County Oregon

1 Response

It is always a good practice to apply a dormant oil spray on your fruit trees in February to help with insect and disease prevention.

Your wormy apple problem is likely caused by the codling moth. The codling moth may be the most damaging insect in home orchards of apples, pears, plums and walnuts. Codling moths begin to emerge when apples are in bloom, usually in May or June. The adults are roughly 3/4 inch across the front wings and are gray-brown with lighter gray lines and golden or bronze areas near the wing tips. The larva or "worm" is about 1/2-inch long, white with a pink hue and a brown head.

Newly hatched larvae bore into developing fruit, feed for about three weeks, leave the fruit, pupate and emerge as adults about two weeks later (the second generation). Depending on location and length of the growing season, two to four generations can occur each summer.

The traditional control program is to spray trees with insecticide. Apply a first cover spray about 10 days after full petal fall (all petals are off) or 17 to 21 days after full bloom. Insecticides must be timed to target newly hatched larvae before they bore into the fruit. Multiple sprays are often necessary with applications up to every 10-14 days; however sprays can be reduced by monitoring for adult moths with monitoring traps or use of degree-day models (see description above) to properly time insecticide applications to the hatching larvae during the growing season.

But if you prefer to use greener methods, the following can reduce codling moth damage.

Pheromone lures and traps.

Pheromone traps are made by attaching pheromones to a sticky bottom trap. Male moths are attracted to the scent and get stuck to the board. The traps monitor moth flight and indicate when you need to spray; only when it is necessary and most effective. If there are no other hosts (apples, pears, plums or walnuts) in the area, sometimes a large number of traps can attract and kill most of the males, significantly reducing breeding.

Sanitation and Banding
Sanitation is the most important practice that is environmentally safe (or safer). If you remove and dispose of damaged young fruit throughout the season, you can help reduce future generations. Larvae continue to feed inside the fruit after it falls from the tree. Remove fruit promptly.

Installing bands covered with Tanglefoot ™ (available from garden supply stores) around the trunk of your fruit trees, 18-24 inches from the ground, can also reduce populations. Mature larvae move down the tree in search of a place to pupate and can be trapped in the sticky substance. While this method reduces the population, it does not provide complete control because many larvae overwinter on the ground.

Attached are some publications you will find useful.

https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1005.pdf

http://extension.oregonstate.edu/gardening/node/1026

http://www.extension.umn.edu/garden/yard-garden/fruit/pears-in-home-garden/

Hope this helps!

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