Peachtree borer is a clearwing moth that attacks the base of trees in the genus Prunus. This includes not only peaches, plums, and cherries but also their landscape relatives, purple leaf plum, and flowering cherry, peach, and plum. The white, legless, full-grown larvae are about 3/8 inch in diameter and over 1 inch long. They attack at and just below ground level, tunneling just under the bark in the cambium. The tree reacts by producing large quantities of sap, called gummosis in the fruit trade, at the base of tree. Eventually, the tree is girdled and dies.
In the landscape, these trees are short-lived. Peachtree borer typically attacks older trees that are in decline from old age. Treatment of these trees is only delaying their death by a couple of years. As such, treatment is usually not in the best interest of the client. This borer can attack young transplanted trees, but these trees usually adapt to site so quickly that treatment may not be needed. Scout young trees for signs of attack before treating, or only treat trees planted in poor situations where establishment is likely to be a struggle.
If insecticide application is desired, apply permethrin (Astro) to the trunk of landscape trees now in southern Illinois. Apply at the end of June in central Illinois; apply in mid-June in northern Illinois. Spray heavily enough to allow the insecticide to run in along the trunk at ground level. Repeat the application 4 weeks later.