Controlling codling moths is all about timing - East Idaho News
In the Garden

Controlling codling moths is all about timing

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We have been getting a lot of calls about when to spray for codling moth. The answer is, not yet. My apples trees in Rigby are barely at the silver tip stage.
Last year codling moths were late emerging because of the cold weather. This year they are delayed even more.

First, the overwintering larvae need to pupate and develop into adults. The adults then mate and start laying eggs. Then, the eggs must develop and hatch young codling moths. This development of codling moths is driven by temperatures. When evening and night temperatures fall below 50 degrees, moths are inactive. As evening and night temperatures rise above 60 degrees, activity increases.

This temperature dependence is also why you can’t just time your sprays on blossom development or petal drop. Different apple cultivars have different bloom schedules. Besides, a few cool days or very warm days can drastically slow down or speed up the development of the codling moth.

In most of eastern Idaho codling moths have two generations per year. Warmer areas may have part of a third generation, and areas like Ashton or Driggs may only have one.

Here are some practices that may help reduce codling moth damage.

Sanitation

Clean up leaf litter and aborted fruit around your trees.

Thin Fruit

Apples and pears should be thinned when they are about the size of a nickel.

Bag Fruit

Early-season eggs are mostly laid on the leaves rather than the fruit. When the fruit gets about one-half to one inch in diameter, they can be bagged. This can be a special paper bag (Japanese apple bag) designed for this purpose or just nylon footies, like you find in the shoe store.

Nylon footies dipped in a kaolin clay solution are more effective against codling moth than just the nylon. Bagging will eliminate much of the codling moth damage and can be combined with one initial coverage with horticultural oil or insecticide before putting them in place.

While bagging takes time, it only needs to be done once, reduces the total amount of insecticide used, and eliminates the chance that later insecticide applications will harm beneficial insects.

Insecticides

Timing is critical for good control without wasting resources. Because the eggs hatch over a period of time and there are multiple generations, insecticides must be applied several times through the summer.

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Adult codling moth | Whitney Cranshaw, Colorado State University, Bugwood.org

The Eastern Idaho Pest Alert Newsletter provides spray timing information throughout the season for areas from Burley to St Anthony and Driggs. If you wish to receive the weekly emailed pest alert, send an email to bonneville@uidaho.edu. We do not share or sell our lists.

Master Gardener Plant Promotion

Idaho Master Gardeners of Bonneville County have one fundraiser a year to help fund several gardener-education projects. Proceeds from the Plant Promotion support educational activities and service projects such as booths at Earth Day, the Eastern Idaho State Fair, Plant Diagnostic Clinic and Water Festival; as well as community garden support for the Japanese Friendship Garden, Master Gardener Demonstration Garden and the new Master Gardener Teaching Orchard.

Come visit with some Master Gardeners and maybe buy some unique flowers or vegetables at the Plant Promotion on May 13, from 8:30 a.m. to 12 p.m. at the Bonneville County Fairgrounds out by Sandy Downs.

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