Peachtree Borers:

There are very few times I suggest a routine pesticide application without knowing that a pest is present. There are exceptions to most rules and I’m breaking this one. The reason is that there is one generation per year of peachtree borer and the timing of their annual activity is predictable within a narrow window of opportunity. And after that, it they have infested a tree, there is little to nothing we can do. The damage can be very serious, can recur year after year, and can eventually be fatal.

Peachtree borers are caterpillars of a clearwinged moth. The moths closely resemble paper wasps; but being moths, they do not sting. These moths emerge throughout the growing season, but the great majority of them are in flight between August 15 and September 15. Consequently, most of the borers can be preventively controlled by spraying the trunk with cyfluthrin or other pyrethroid insecticide around August 15 and again about 2 weeks later. The moths lay eggs at the base of peaches, plums, and cherries including ornamental cherries.

From these eggs hatch tiny, white caterpillars that bore into the bark and tunnel in the cambium at the base of the tree. If many borers infest a tree, the cambium may be completely girdled beneath the bark, and the tree will die. Evidence of borers, generally found at the base of the tree or lower trunk, includes oozing sap or loose bark. (Neither of these is proof that borers are or have been present. Lawnmowers and string trimmers can create the same symptoms.) When borers are present, they pupate inside the infested tree during late spring and summer and then emerge as moths a few weeks later. The prevailing recommendation is a spray to prevent further borers from invading the tree if this is a problem. There is not a simple method to control larvae already boring in the wood. You make the call.