Peachtree Borer, Lesser Peachtree Borer, Shot Hole Borer
Both the Peachtree Borer and the Lesser Peachtree Borer are clearwing moths. They are often mistaken for wasps due to their appearance and behavior. Shothole borers are small, cylindrical beetles.
The female Peachtree Borer is metallic, blue-black except for a red-orange band on the abdomen (Fig. 1). The front wings are blue-black and the hindwings are transparent. The male Peachtree Borer has clear wings with a black border. The body is black with yellow stripes along the back at the base of each wing. There are narrow yellow stripes on the abdomen. The larva is about 1 to 1 1/4 inches long when fully grown. It is creamy white with a brown head (Fig. 2).
Both the male and female Lesser Peachtree Borer resemble the male Peachtree Borer, but are somewhat smaller. The larva is very similar, but smaller.
Hosts: Both the peachtree borer and the lesser peachtree borer are serious pests of peaches. They are found on most cultivated and wild stone fruits, including some ornamental shrubs such as flowering peach and cherry. Shothole borers attack many fruit trees and ornamental trees and shrubs. Plants under stress are highly susceptible to shothole borer attack.
Injury: As the common name indicates, both are borers during larval stage. The Peachtree Borer attacks the tree at the base and may be found feeding from the main roots to about 10 inches up onto the trunk. Masses of gum with sawdust-like material, called frass, mixed in with the gum are the primary symptoms of attack. Young trees can be killed by a very small number of larvae. Older trees can tolerate more larvae.
The Lesser Peachtree Borer attacks the trunk and main limbs. Again the symptoms are gum containing frass oozing from the area. Heavy infestations can kill individual limbs or an entire tree.
Shothole borers attack the trunk and limbs. The entry holes look like the tree has been hit with fine bird shot (Fig. 3). The adult beetle bores into the bark and then carves out chambers below the bark in which to lay eggs. The larvae feed on the bark. Occasionally, shothole borers may attempt to enter the twigs at the base of flower buds. This can destroy the buds.
Life History: All three borers overwinter as larvae. The Peachtree Borer has one generation per year. Some adults begin emerging in late May. The number emerging slowly increases in June and July and then increases rapidly to a peak in mid- to late August. Few adults are found after mid-October. About two weeks after the eggs are laid at the base of the tree the small larvae hatch, burrow into the bark, and begin feeding. They stop feeding when cold weather comes and resume feeding the following spring. When mature, they form a cocoon of silk and frass in a tunnel in the soil or bark of the tree.
Pupation takes place in the cocoon. Just before the adult emerges, the pupa wiggles out of the tunnel so that about a third to a half of it is exposed to the air. After the adult emerges, the golden brown pupal skin is left protruding from the soil or bark.
The lesser Peachtree Borer has a very similar life history. The only difference is that there are two generations per year. Occasionally there may be a partial third generation. Emergence peaks occur in mid-May and late July. Females of both borers are attracted to damaged areas on the bark.
Shothole Borers have several generations a year. The adults emerge from the infested trees and move to new trees, especially those under stress from drought, disease, or other reasons.
Control: Since the Peachtree Borer causes its most severe damage to young trees, special care must be taken during planting to avoid damaging the bark. A pre-plant dip in an insecticide solution is strongly recommended. In light soils the wind may make the tree move enough to make a gap between the trunk and the soil or abrade the bark. This is also an excellent entry site for the larvae. Annual trunk sprays during August will generally keep the Peachtree Borer under control. Be sure to apply sufficient spray from the scaffold limbs to ground level so the bark is saturated and a small puddle forms at the base of each tree.
The best control for the Lesser Peachtree Borer and Shothole Borer is to keep the trees in a vigorous, healthy growing condition and to prevent mechanical injury. Prune out split or broken limbs and limbs with signs of borer damage where feasible. Avoid spreading bacterial canker while pruning.
Spray infested sites while applying the trunk sprays in August. This will help reduce the Lesser Peachtree Borer and Shothole Borer population. Because there are two or more generations per year it is difficult to get good control with insecticides since the first generation emerges while there is fruit on the tree.
A directed, hand applied spray is the only effective method of application. Commercial growers have several insecticide options for borer control, but homeowners and small growers are much more restricted in what can be applied. Check with your local County Extension Agent for specific insecticide recommendations.
If a tree is gumming, but no sawdust-like frass is found, contact your County Extension Agent about disease control recommendations. This may be a sign of potentially serious disease problems.