Garden Detective: That’s no disease – it’s codling moths

10/26/2013 12:00 AM

10/24/2013 4:27 PM

In the backyard, we have several fruit trees. One of them is 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. Any help would be greatly appreciated.

Alex Valle, Sacramento

Your apple tree will be fine. It’s not disease; it’s a classic case of codling moth, a common malady of backyard apple and pear trees in our area.

It’s not the mature moth but its voracious larvae that do the damage. Codling moth larvae are white to light pink “worms” with a dark brown head. They are one of the few worms that are likely to be found inside pear or apple fruit.

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

They can cause substantial damage, often infesting 20 percent to 90 percent of the fruit on a single tree.

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

UC 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 1 1/2 quarts. Pour the mixture into the jug and hang the open jug in the tree.

It won’t eliminate every moth, but it makes a big dent in their population. 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.

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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