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FS ShieldForest Health Protection, Southern Region


Tetralopha robustella Zeller

Importance. - The pine webworm occurs in southern Canada and throughout most of the eastern half of the United States and attacks pitch, Virginia, white, shortleaf, longleaf, loblolly, and slash pines. The pine webworm usually attacks one and two year seedlings, but will infest saplings and large trees. Rarely is defoliation severe enough to kill the seedlings, but it may have some growth impact.

Identifying the Insect. - The adult moth is dark to medium gray, with dark gray to black forewings on the basal third and outer half. Wingspread is approximately 1 inch (25 mm). The larvae are light gray with darker tan stripes along the body. They are approximately 3/4 inch (18 mm) in length when fully grown. The pupae are reddish in color and approximately 1/2 inch (12 mm) long.


Larva. (Click for detail. JPG 18K).

Identifying the Injury. - The most noticeable sign of attack, and usually the first, is a large mass of frass and excrement pellets entangled in a network of silken webbing. Close examination of this mass of material will usually reveal one or more larvae.

Biology. - Eggs are usually laid on seedlings, or occasionally on larger trees, between May and September. After the eggs hatch, the caterpillars live in silken webs surrounded by masses of frass and feed on the needles. After feeding is completed, the caterpillars drop to the ground and pupate in the soil. In the South, there are usually two generations per year.

Control. - In plantations, hand-picking is an effective method of control. When high value nursery stock becomes infested, chemical control may become necessary.

Frass and excrement pellets entangled in webbing

Frass and excrement pellets entangled in webbing. (Click for detail. JPG 32K).