Alex Valle

What’s eating these Granny Smith apples? It’s that familiar pest: larvae of the codling moth. Action now can diminish their impact on your backyard harvest.

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Garden Detective: Codling moth larvae are eating his apples

Published: Saturday, May. 31, 2014 - 12:00 am

In the backyard, we have several fruit trees, including a Granny Smith apple tree. My problem is that the tree is infected with some sort of disease. I’ve tried different pesticides but they don’t seem to help. I’ve attached a couple of pictures of the fruit. I would like to know if there is anything I can do to save it.

– Alex Valle, Sacramento

According to UC master gardeners, the larvae of the codling moth are infecting your apples. These larvae penetrate apples and pears, and tunnel to the core, leaving holes in the fruit that are filled with reddish-brown crumbly droppings called “frass.”

Codling moth larvae are white to light pink worms with a dark-brown head. They are among the few worms that are likely to be found inside pear or apple fruit. They can cause substantial damage, often infesting 20 percent to 90 percent of the fruit on a single tree.

But codling moths often can be kept to tolerable levels by using a combination of nonchemical management methods.

Pest Note 7412, devoted to codling moths, lists both nonchemical and chemical strategies for controlling these pests, including a homemade trap and lure that uses vinegar, molasses, ammonia and water.

Keep the traps in the trees from late April through late September, because there are up to six generations of these insects every year here in the Sacramento region.

Here’s the recipe: First, get a 1-gallon plastic milk or water jug. Mix together 1 cup cider vinegar, 1/3 cup dark molasses and a dash of ammonia. Add enough water to this mixture to make 11/2 quarts. Pour the mixture into the jug and hang the open jug in the tree.

The late Bill Pierce, who wrote Garden Detective answers for decades, swore by the homemade codling moth solution.

“I have used this trap with good results; it is easy, cheap and effective,” Pierce wrote. “It will not eliminate all of the codling moths, but you will get more worm-free fruit than wormy fruit.”

In addition to the traps, remember to clean up any fallen fruit and leaves. Fruit on the tree can also be individually bagged to deter the pests.

Thinning out and removing infested fruit on the tree is an especially important part of an integrated pest management program against the codling moth, say master gardeners. Pruning trees to a height at which the canopy is easy to reach also will facilitate management of this pest.

The Fair Oaks Horticulture Center hosts a variety of workshops for the home gardener, including pruning fruit trees. The workshop schedule is available at ucanr.org/sacmg.

Read what master gardeners have learned about codling moth management at the Fair Oaks Horticulture Center at ucanr.edu/sites/sacmg/orchard.

Information on the codling moth is available at www.ipm.ucdavis.edu. This information also is available by sending a self-addressed, stamped business-size envelope to: Pest Note 7412, UC Cooperative Extension, 4145 Branch Center Road, Sacramento, CA 95847.



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