How to reduce codling moth damage in your apples, pears and other fruits

The most common apple and pear flesh-feeding insect in eastern Idaho is the codling moth. This spring, the codling moth emergence and egg-laying has been delayed about three weeks due to chilly spring weather.

Codling moths tunnel through the flesh and feed primarily on the seeds. The entry tunnels are small. Large tunnels are an indication of an exit tunnel. They are often the same tunnel.

They overwinter in leaf litter, bark crevices, and other protected locations as mature larvae in a cocoon until early spring, when they pupate. They emerge as adults and begin their mating and egg-laying activities usually about the time red delicious apples bloom.

When evening and night temperatures fall below 50-degrees, moths are inactive. As evening and night temperatures rise above 60-degrees, egg laying activity increases. Egg development is also affected by temperature.

This temperature dependence is 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. Warmer areas may have part of a third generation, and areas like Ashton or Driggs may only have one.

Use as many of the following options as you can to reduce codling moth damage in your apples and pears.

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. This topic will be covered in a future article.

Bag Fruit

Early-season eggs are mostly laid on the leaves rather than the fruit. When the fruit gets about one-half – 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.

The paper bags have a tie to attach them to the fruit. For the nylon footies, you can use tiny hair bands to help hold them in place. Nylon footies dipped in a kaolin clay solution are more effective against codling moths 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.

Paper bags affect the mature fruit color and should be removed a couple of weeks before harvest. Depending on how early in the season this is, there may be some late-season codling moth damage. The nylon footies do not adversely affect mature fruit color.

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.

The Eastern Idaho Pest Alert Newsletter will provide spray timing information throughout the season for areas from Burley to St. Anthony and Driggs. Once mating moths are trapped in an area, the date is entered into a degree-day model, which helps determine the best time to spray for codling moth control.

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.