Trunks and limbs of peach and plum trees may be severely injured by the lesser peachtree borer. The feeding of the borers in the wood weakens or kills the tree or limbs and provides entry for rot-producing organisms and shot hole borers. Unlike the peachtree borer that attacks the trunk of the tree, the lesser peachtree borer is most often found in the scaffold limbs of the tree.
How to Identify Damage
The damage from the lesser peachtree borer can be identified as masses of gum mixed with frass and sawdust exuding from the feeding areas under the bark of scaffold limbs. Probing in these areas to locate the larvae will separate lesser peachtree borer damage from similar damage caused by machinery, disease organisms or weather causing factors.
Identification of the Larvae and Life History
The larvae or borers have white bodies and dark brown heads. They are about an inch long when fully grown. They feed under the bark around wounds, usually in the upper trunk and in branches. However, they may be found near the base of the tree. When the larval stage is completed, flimsy cocoons covered with frass are constructed under the bark near the edge of the wounds. Shortly before transforming into moths, the pupae work their way partly out of their hiding places. When the adults emerge, they leave their pupal skins protruding from the bark surface. The moths are active during the day and the females deposit eggs on rough bark at the margins of wounded areas. The first adults appear in March. Peak emergence is not reached until early May. Larvae hatch from eggs deposited by these adults and feed throughout the summer. Many of the larvae pupate and appear as the second generation adults in late summer and early fall with most individuals emerging in September. The remainder of the larvae stop development in the sixth instar; pass the winter in their feeding areas under the bark; pupate; and emerge into adults the following spring.
Lesser peachtree borers are seldom a problem in well tended orchards. They are attracted to the damaged areas of the tree which is usually the result of poor cultural practices. Careless pruning techniques provide many favorable sites for egg laying around stubs of branches. Branches broken because of insufficient thinning of the fruit and wounds arising from barking the tree with equipment during cultivation and harvest also are attractive to lesser peachtree borers. Prevent sun scald areas by leaving small branches to shade larger limbs. Winter injury of trunks and scaffold branches and cracked limbs resulting from scale infestations also provide sites for larvae feeding.
To assist the tree in preventing lesser peachtree borer infestations, clean all damaged area thoroughly and paint with a tree paint. Prior to painting, be sure to remove all debris and rotten wood from the wound.
LESSER PEACHTREE BORER CONTROL MEASURES
Several insecticides used for other peach insects will also effectively control lesser peachtree borer larvae. Use of these materials during the normal spray program in April and May will suppress this insect. Older trees that are weak and have cracked and sun scalded limbs are more susceptible to injury. In these and heavily infested orchards, two additional sprays in August or September may be needed for effective control.
Keep trees healthy and as free as possible from wounds, cankers and weather injury. Prepare this solution by dissolving two pounds of PDB and one gallon of missable dormant oil and diluting with two gallons of water. Treat only affected areas and do not circle the entire trunk or limb with the solution. Apply on a warm, sunny day after trees have shed all foliage and there is no fruit on the tree. Usually November or December is best. Do not use crystals containing napthalene.
If you are following a spray schedule, sprays applied for control of fruit infesting insects during April and May are effective in reducing populations of lesser peachtree borers. However, inspections of the limbs in the fall may reveal the need to apply a mixture of PDB and oil in the dormant season.