Codling Moth (Cydia pomonella)

What are codling moths?

Codling moth larvae are the "worms" in "wormy apples" (lower right). Codling moth adults are small grey moths with a coppery-colored band on the end of the wings (upper right). Codling moth larvae are probably the most important insect pests of apples, pears and walnuts, worldwide. Larvae infest the fruit or nuts and can damage a significant percentage of a crop if not managed.

There are 2-4 generations of codling moth per year depending on the length of the growing season. Adult moths first emerge in late spring. After mating female moths lay eggs on branches and leaves, later generations lay eggs on fruit as well.

Hatching larvae immediately bore into the fruit, or nuts, and begin feeding on the seeds. Feeding damage can be extensive and may render the fruit or nuts useless. After completing development they exit the fruit or nut and seek a place to pupate either below the tree or under bark scales. Emerging female moths use a sex pheromone to attract male moths prior to mating (see below).

Can codling moth damage be prevented without insecticides?

Commercial fruit and nut growers use insecticides, traps, and mating disruption pheromones to protect orchards against codling moths. Homeowners can use many of these same techniques but on a smaller scale.

Step 2 -- Use pheromone traps to capture as many male moths as possible. Hang at least one trap per tree, but two to four in a large tree is better. These traps emit a scent (pheromone) that lures male moths onto a sticky surface. Traps can be very effective for disrupting moth mating and for timing other control activities. Hang traps soon after bloom.

Step 3 -- Once pheromone traps begin catching moths apply your first spray of horticultural oil within a week. Use a 1 or 3 gallon (depending on tree and orchard size) sprayer. This oil will kill eggs and young larvae on the surface of fruit and branches. Repeat oil sprays as directed on product label until all fruit is picked.

Step 4 -- Another very effective, but time consuming, method is to simply bag individual apples or pears on the tree. This will prevent moths from laying eggs on new fruit. Bag fruit 4-6 weeks after bloom but only fruit that shows no evidence of infestation. Use regular, paper, "lunch"-style bags. Cut a small slit in the bottom of the bag, place fruit through slit and staple the oher end shut. You may want to bag only enough fruit for your fresh needs. Bags should be replaced if damaged by rain or sprays, etc.

Control of codling moth with sprays

The conventional treatment for codling moth is to spray trees every 10 days to 2 weeks following fruit set with an insecticide that kills eggs and newly hatched larvae. Home orchardists have resisted this method because of the toxicity of the insecticide. Recently, however, a new class of low toxicity organic insecticide, called spinosads (right), has been introduced that home gardeners can use safely.