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Pine false webworms make small silken nests on pine branches.

Pine False Webworm

Adult pine false webworm is a sawfly, not a caterpillar which would be the larva of a moth.

Species: Acantholyda erythrocephala (Linnaeus)


Distribution:

Originally Europe, this pest has spread over most of the northeastern United States.


Hosts: Prefers red and white pines but will infest Scotch and several other pines.


Damage:

Light infestations are unsightly because of the frass-filled nests on branch tips. However, heavy infestations can remove most of the older needles from the trees. Seedlings are occasionally attacked which results in death to a few individuals.


Description and Life Cycle:

In the field, this pest looks very much like the true pine webworm. However, the pine false webworm makes smaller nests and usually has under a half dozen larvae per nest. Also, there are no silken tunnels or runways present.

The pine false webworm overwinters as a mature larva (prepupa) enclosed in a cocoon in the ground. At the first hint of spring, March and April, the prepupae form the true pupae and the adults emerge three to four weeks later. The adults are dark metallic blue-black in color and the females have red-orange heads. After mating, the females lay groups of two to six eggs lined up on needles. The larvae hatch and move to the bases of last year's needles. Here they construct loose webbing and feed by cutting off needles and dragging them into the nest. The larvae look like caterpillars, but are green with two small antennae-like projections sticking out from the tip of the abdomen.

By late May and early June, the larvae are through feeding and the nests have become full of pieces of dead needles and fecal pellets, frass. The mature larvae drop to the ground, burrow in and remain dormant until the following spring.


Control Hints:

This pest is not well understood and populations fluctuate from year to year. The larvae form the nests so early in the spring that they are often unnoticed until development is finished. Early inspection of the plantation is important.

Option 1: Cultural Control - Pruning of Colonies - Small numbers of nests can be easily pruned out or destroyed by hand.

Option 2: Chemical Control - Insecticide Sprays - Extensive infestations, especially in seedlings or on trees ready to harvest are most easily controlled through spraying. Spray when nests are first seen.