Catch codling moths early

Look for the telltale frass, as seen on this Granny Smith. Remove that apple and eliminate a codling moth larvae, too. (Photo: Debbie Arrington)

This pest attacks apples, pears, walnuts

By Debbie Arrington

If you've ever bitten into an apple and found a little pink worm, you've encountered codling moths.
That worm is the moth's very hungry larva. It tunnels through the apple's flesh, creating ugly brown scars.

Eventually, the apple -- or the larva -- falls to the ground, where the moth continues its life cycle.

Codling moths love apples but also attack pears and English walnuts. Their damage is becoming very visible now.

Notice any odd holes on the side of baby apples? The holes may be topped by little brown piles. That's frass, reddish-brown droppings from the larva as it bores into the fruit.

If left uncontrolled, codling moths can infest 20% to 90% of a tree's fruit. Late-developing varieties tend to be hardest hit.

Codling moths can have three or four generations a year. In Sacramento, we're likely on generation 2. According to the UC Cooperative Extension master gardeners, codling moths overwinter as full-grown larvae in silky cocoons wedged under the tree's bark. The adult moths emerge in April. They start mating when temperatures reach 62 degrees at sunset, the only time they're active.

That makes these moths hard to trap or fight with pesticides.

The best ways to limit codling moth damage are sanitation and exclusion, say the master gardeners.
Sanitation means picking up and discarding fallen fruit. Check your tree every two weeks and look at the developing fruit. Remove and destroy any infested fruit showing frass holes; the larvae is still inside. That will cut down the next generation. That thinning has the added benefit of encouraging remaining fruit to grow bigger.

Bagging the baby fruit can exclude the moths and larvae. It's tedious and nearly impossible with a large tree but very effective especially on smaller trees. Master gardeners suggest using paper lunch bags. Cotton bags with string ties also work.

Trapping can reduce populations on isolated trees, but isn't a reliable way to reduce damage, say the master gardeners.

Because codling moths can get around, enlist neighbors with apple, pear or walnut trees to fight moths, too. That can help reduce their toll and increase everyone's harvest.

For more information including bagging instructions: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7412.html.