Pine false webworm

Latin name: Acantholyda erythrocephala (L.)
French name: Pamphile introduit du pin
Order: Hymenoptera
Family: Pamphiliidae

Distribution

Canada

This is an introduced exotic insect that was first found in Ontario in 1961, currently found throughout much of Ontario, especially in the southern region.

Micro-habitat(s)

Soil, Leaf

Damage, symptoms and biology

The larvae construct silken tubes along the branch from within which they feed by attaching silk strands to needles, cut them off and pull them into the webbing. The tubes soon fill with partially consumed needles, frass, and cast skins. Older larvae disperse and feed singly from within individual silken tubes. The larvae feed primarily on old foliage. If all the old foliage on a tree has been consumed, they will feed on the current year’s needles.

There is one generation per year. Mature larvae have yellowish coloured heads, with small dark-brown spots. The body is pale greenish-gray, with purplish red longitudinal stripes along the sides and back. Adults emerge in late April or early May, mate, and the female lays her eggs on last year's needles. The larvae hatch in approximately 2weeks, crawl to the base of the needles and begin to feed. Feeding is completed by mid-to late June and the mature larvae drop to the ground and hibernate in earthen cells.

Other information

Before 1993, damage in Ontario was confined to trees less than 6 m in height and whole tree mortality was rarely reported. In 1993 severe defoliation of semi-mature red pine, 15 to 20 m tall, was reported at two locations in Ontario. Following 3 to 4 years of severe defoliation whole tree mortality levels, up to 60%, have been reported in these semi-mature plantations. Consecutive years of severe defoliation (>70%) will result in an overall loss of growth and vigour and cause whole tree mortality. Severely defoliated red pine are susceptible to attack by bark beetles, Ips sp., and Armillaria root rot, Armillaria ostoyae (Romagn.) Herink.

Natural controls include parasitic insects, birds and rodent predators. On young, open-grown ornamentals, larvae can be removed by hand and destroyed.

Canadian Forest Service Publications

Pine false webworm

Diet and feeding behaviour

  • Phyllophagous: Feeds on the leaves of plants.
    • Webworm: Spins a silk shelter in which to hide or feed.

Red and eastern white pines are the preferred hosts; also feeds on jack, Scots, Austrian, mugo, and Japanese red pines

Main host(s)

Austrian pine, eastern white pine, jack pine, Japanese red pine, mugho pine, red pine, scots pine