Peach Tree Borers
Lesser Peachtree Borer Sanniniodea exitiosa
Peachtree Borer Synanthedon pictipes
Description
Figure 1. Peach Tree
Borer Larva
The female moth of the peach tree borer is dark blue with a wide orange stripe around the abdomen. She has opaque front wings and clear hind wings. The male is steel gray with yellow markings and clear wings. The male and female moths of the lesser peach tree borer have clear wings, and both are metallic blue with yellow markings. The eggs of the lesser peach tree borer are small, reddish-brown, and extremely hard.
Figure 2. Peach Tree
Borer Adults
The larvae of both species are naked, grayish-to yellowish-white caterpillars with brown heads. The length varies from very small to about three-fourth inch for the lesser peach tree borer and one inch for the peach tree borer. To spin a cocoon, the mature larva makes a hollow space anywhere near the surface in the wound area. Bits of frass, gum, or bark are attached to the outside. The pupa is a light brown typical moth pupa.
Life History
The larvae overwinter in whatever stage of growth they happen to be when winter approaches. They may be very small or fully mature. They begin to feed when the temperature warms up and grow as the temperature rises during the summer. The mature larvae transform into pupae from early spring to late July. In southern Illinois the lesser peach tree borer moths emerge from late May to late September, the greatest numbers appearing from mid-June to late July. The peach tree borer moths emerge from mid-June to late September with the greatest numbers appearing from mid-July to mid-August.
Since moth emergence is also affected by temperature, it begins later and occurs for a shorter time in northern Illinois than in the southern section. The peach tree borer moth lays eggs at ground level on the trunk of the tree, in cracks in the ground, or on bits of litter. The lesser peach tree borer moth goes up and down the limbs seeking rough bark or cracks in which to lay eggs. Particularly attractive are wounds where gum is exuding and where borers are present. Eggs hatch in 8 to 30 days, and the larvae attempt to bore into the bark. To survive they must get under dead bark near live bark where they have protection for feeding. The peach tree borer completes one life cycle a year. The lesser borer completes about one and one-half cycles a year.
Damage
Any wound on stone fruit trees may cause gum to exude. Borer damage is usually attended by gumming, with varying amounts of frass in the gum. The frass or fecal pellets look like fine sawdust. Peach tree borer injury occurs a few inches either above or below the ground. Lesser peach tree borer injury occurs particularly in peach tree borer wounds but may also occur in any other spot above ground where the larvae can get under dead bark. This may be where twigs or branches have died and where mechanical wounds or winter injury has occurred. The damage is caused by feeding of the larvae on the growing inner bark. The wounds expand rapidly, and limbs or trunks may be girdled. Open wounds permit entry of disease organisms that may also kill live tissue or decay the heartwood. The peach tree borer has long been an important pest; the lesser borer has been important only in the past ten years.