PITCH MASS BORER
(Family: Sesiidae)

The pitch mass borer, Synanthedon pini (Kellicott), a clearwing moth, primarily attacks the trunk and limbs of eastern white pine, but also injures scots, austrian, jack and red pine, along with white, Norway and Colorado blue spruces. Wounded trees, trees growing under stressful conditions, and those previously infested, are preferred. The caterpillar galleries cause defects, which lower the value of the tree for lumber. Abundant and repeated attacks can kill a tree.

The clearwing moth, which bears a resemblance to yellow jacket wasps, lays its eggs in midsummer in wounds, such as pruning cuts, and sometimes on the bark of the trunk or limbs. The larvae tunnel into the inner bark, where a cavity is excavated. They feed on resin exuded from the damaged tissue. The mature larvae reach a length of approximately 25mm. Their body colour is usually near white to pink depending on which tree they are feeding and the food supply. Their brown head is smaller than the prothorax. Due to their extended life cycle, different instar larvae are likely to be found at any one time. Characteristic, large accumulations of pitch and frass, sometimes as large as a small fist, form at the point of attack. New attacks tend to occur at old sites. Pupation occurs within the pitch mss from late May to June. Larvae pupate at a position beyond the pitch, in order for the pupa to release the adult. The clearwing moths appear from the middle to the end of June, although others possibly emerge in July and August depending on the location. Two to three years are required to complete a life cycle.

Control

Since wounded trees are particularly susceptible to attack by the pitch mass borer, it is important to minimize mechanical injuries to the trunk and limbs. Pruning trees during the egg lying period of the pitch mass moth should be avoided.

No chemical sprays are specifically registered in Ontario for the control of the pitch mass borer. However, endosulfan and chlorpyrifos are registered for control of woodborers, and have proven effective in deterring egg laying of similar borers in trunks and limbs of some ornamental and fruit trees. In Ohio, chloropyrifos gave excellent results against several similar Synanthedon borers.

When applying pesticides, the bark of the main branches and trunk should be thoroughly sprayed to the ground level. It is important to time spray treatments for when the adults are laying eggs on the bark surface, and before young larvae penetrate the bark. The insecticides will not kill already established borers. Manually removing the pitch and crushing any existing insects can destroy older larvae and pupae. Severely infested trees should be removed.

Follow label instructions to ensure the safety and efficacy of each product.

W.A. Attwater/M.Sabourin

PDCF-028 (Revised 2003/11/07)