Lesser Peachtree Borer
Description and life cycle
Adults are day-flying moths that resemble wasps. Veins and margins of transparent wings are fringed with steel-blue scales; the body is blue and narrowly fringed with yellow. Males of lesser peachtree borer have yellow scales on the top of the head between the eyes and black scales between the antennae. This combination differentiates them from peachtree borer males, which have black scales between the eyes and yellow scales between the antennae. Lesser peachtree borer larvae are white with a yellowish brown head and reach 1 inch at maturity.
There are two and possibly a partial third generations each year; the first flight occurs during May and June, and the second during August and September. The lesser peachtree borer overwinters as larvae and reaches full growth during April and May. Larvae eat an exit hole nearly through the bark, spin a cocoon, and pupate in a small cavity. In 3 to 4 weeks, a clearwinged moth emerges, leaving an empty pupal skin projecting from the burrow. Adults are active for several weeks. The female moth is capable of laying several hundred eggs in cracks, under bark scales, and in cankered areas. Moths are attracted to trees that have been injured or previously infested. Eggs hatch in a week to 10 days, and young worms move to the inner bark and continue to feed.
Growers first notice evidence of borer infestation by checking for pupal skins in cankered areas. An early sign of lesser peachtree borer injury is the presence of wood chips, sawdust, and frass produced by feeding borers in the gum in cankered areas. If the gum does not contain this particulate material, the injury is probably not caused by borers. As an aid in timing sprays, growers should obtain pheromone trap records on flight activity. Treat at peak flight, usually toward the end of June, if there is an average of more than two borers per tree, and again in late summer. If fewer than two pupal skins are located in each tree, target only the second generation in late summer.
Any horticultural practice that prevents canker and maintains good tree development will help prevent borer damage.
A pheromone is registered for the control of lesser peachtree borer on peach, nectarine, cherry, prune, plum, and apricot. Dispensers release pheromones for 100 to 120 days and should be placed in the orchard before moth emergence in the spring. For effective control of lesser peachtree borer, use the recommended number of pheromone dispensers per acre. To improve the efficacy of mating disruption, distribute the dispensers uniformly throughout the entire block.
High-volume handgun sprays thoroughly wetting trunk and scaffold limbs are necessary, with at least 1 gallon of spray mixture applied per tree. The late summer spray can be applied after harvest. If peachtree borer is also a problem this spray should be made within the first 2 weeks of September. If only lesser peachtree borer is present, sprays may be applied to late maturing varieties in early August. Do not allow spray residue to contaminate fruit. Specific chemical recommendations for home gardeners are in Fruit Production for the Home Gardener, and recommendations for commercial growers are in the Penn State Tree Fruit Production Guide.