Purge the peach trees of pests | TribLIVE.com
Jessica Walliser, Columnist

Purge the peach trees of pests

Jessica Walliser
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Peach trees and their developing fruits are prone to several different pest issues.

Question: We have two peach trees in our backyard and we have two different issues going on that keep us from seeing any ripe fruit. Can you advise us on what’s going on and how to handle it? First, there are holes in the growing peaches. When you crack one open, there’s a little worm inside. Second, there is sticky sap leaking out from a few spots at the base of both of the trees.

Answer: Peaches are among the most difficult tree fruits to grow. They’re susceptible to several different pests, in addition to a few diseases such as brown rot (which leads to rotten fruit) and peach leaf curl (which leads to contorted, discolored foliage).

Despite the challenges in growing them, homegrown peaches are well worth the effort. Their sun-ripened flavor is spectacular, and each tree’s productive life is typically between 12 and 15 years.

It sounds like you’re dealing with two very common insect-related issues peach growers face in Pennsylvania. Let’s look at each one of them.

The small holes and tiny worms you’re finding on and in the peaches themselves are likely to be codling moths. These moths attack not just peaches, but also apples, pears and quince. Female coddling moths lay eggs on developing fruit or leaves, and in a few weeks, the newly hatched larvae create tunnels inside the fruit. They often are found near the core feeding on the seeds. These tiny caterpillars then leave the fruit through a separate exit hole, drop to the ground to pupate into an adult, and start the cycle again, often producing two generations in a season.

The best preventative method for codling moths is to use pheromone traps to lure and capture the adults. These traps are hung in the trees a few weeks before the flower buds open. They need to be replaced in July to control the second hatch. Two traps per full-sized peach tree will suffice.

There are insecticides that work to control codling moths, but many of them are harmful to bees and other pollinators. One natural spray that’s quite effective in preventing codling moths from laying eggs on your peaches is kaolin clay. Kaolin clay is a mined mineral that’s used in everything from toothpaste to antacids.

Sprayed on the fruit as a liquid, this wettable powder dries to form a thin, powdery coating on the fruit, repelling the adult moths and preventing them from laying their eggs. Begin spraying the tree at petal drop and continue to do so every 7-10 days for about eight applications. The trees look a little funny coated in the white spray, but it’s worth it.

Your second issue sounds much like peach tree borers. The larvae of a different species of moth, peach tree borers attack not only peach trees, but also plums, cherries, nectarines and apricots.

Adult moths lay eggs on the bark of the tree in mid- to late summer. The newly hatched larvae burrow under the bark, tunneling between the inner bark and the sap wood, causing the tree to lose vigor. If there are multiple borers per tree, it can cause decline and eventual death. The globs of sticky sap you see leak out of their entrance holes throughout the growing season. The larvae overwinter in the tree, then emerge from an exit hole as adults early the following summer.

Pheromone traps are useful to capture and monitor adult peach tree borers. But the best method for controlling the borer is to carefully examine the tree trunk for small holes with bits of sawdust coming out of them every fall. If you find an entrance hole, push a piece of straightened wire in, as far as it will go, to squash the borer.

Another option is to inject a specific species of beneficial nematodes (Steinernema carpocapsae) into the hole using a needleless syringe. The USDA’s Agricultural Research Service found that an application of nematodes was able to control peach tree borers as well as synthetic chemical applications in small field trials.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to [email protected] or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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