Now is the time to protect peach trees from pesky borers

Published 12:00 am Sunday, July 19, 2009

One of the nurses over at the Family Medical Clinic on Mission 66 has nicknamed me bug man.

While not technically an entomologist by training, I do get my share of experiences with insects on a fairly routine basis. This past week was certainly no exception.

An Extension client from Marion Park brought in suspected insect-damaged pine tree buds; one of the Master Gardener interns delivered a sample of galls formed by cypress twig gall midges from a bald cypress tree; and yet another client brought in a sandwich bag of lice combed out of the hair of a few young girls. Perhaps one of the timeliest insect questions of the week, however, came from a National Park Service employee who attended a safety meeting Tuesday morning. Following that meeting, he sought answers to some questions he had about controlling peach tree borers in his orchard.

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I am really glad that he asked the questions now, as it is very near the proper time to begin protecting peach trees from these damaging pests. In fact, peach tree borers can also attack plums, nectarines and even some ornamental trees, such as cherry laurel, flowering cherries and purpleleaf plums. 

Many of you have seen the evidence of peach tree borer damage — the gummy, frass-filled exudate at the site of the attack. Actually, there are two species of peach tree borers — one simply called the peach tree borer (Synanthedon exitiosa) and the other, called the lesser peach tree borer (Synanthedon pictipes). Peach tree borers focus their attack on the lower 10 to 12 inches of the trunk to around 3 inches below ground level. Lesser peach tree borers attack higher on the trunk and on larger scaffold limbs.

Peach tree borer moths lay eggs on the tree’s bark near the ground, especially around injured areas. The eggs hatch in about seven days and the larvae bore into the bark where they feed on the cambium, growing to about an inch in length. Their feeding weakens the tree, and infestations by multiple larvae can girdle even larger trees.

The key to controlling peach tree borers is to kill the newly hatching larvae before they bore into the bark. To do this, one must spray with an insecticide at the proper time of year. Since peach tree borer moth flights become heavy in August, late July to early August is the best time to begin treatments.

A couple of the standard insecticides that were used to control peach tree borers in the past — Lorsban and Thiodan — are no longer labeled for homeowner use. The best option is to use an insecticide containing permethrin, such as Hi-Yield Garden Pet and Livestock Spray, and apply it as a basal spray every two weeks through September. Maintaining healthy, vigorous trees, pruning properly and avoiding mechanical injury to the bark will help make trees less susceptible to peach tree borers, too.

John C. Coccaro is county Extension director. Write to him at 1100-C Grove St., Vicksburg, MS 39180 or call 601-636-5442. E-mail him at