Pine false webworm
Information about pine false webworm (Acantholyda erythrocephala), a forest defoliating insect found in Ontario.
- Invasive – native to Europe and Asia.
- Pine false webworm was first collected in Ontario in 1961.
- Prior to the early 1990s, this pest rarely affected mature host trees and was considered a chronic problem of young pines prior to crown closure.
- In 1993, larger scale infestations began to occur on mature eastern white pine and red pine stands.
“Invasive” refers to a species that has moved outside of its native habitat and threatens the new environment, economy or society by disrupting local ecosystems.
Red pine (Pinus resinosa) and eastern white pine (Pinus strobus) are the preferred hosts; however, pine false webworm will also feed on jack pine (Pinus banksiana), Scots pine (Pinus sylvestris) and Austrian pine (Pinus nigra).
Species identification and life cycle
- Adults emerge in late April to early June from the soil where they overwintered.
- Upon emergence, adults mate and the females lay eggs in previous years’ needles.
- The female uses her saw-like appendage to cut into the needle where eggs are deposited; eggs hatch in approximately two weeks.
- Mature larvae have yellowish coloured heads, with small dark-brown spots and purplish red stripes along the sides and back.
- Larvae construct silken tubes along the branch and feed by attaching silk strands to needles, cutting them off and pulling them into the webbing.
- Feeding is completed by late June to early July, and the mature larvae then drop to the ground and hibernate in earthen cells.
- While some pine false webworm can complete development from egg to adult in one year, a percentage of the population takes two years to mature.
Symptoms and damage
- Larvae feed initially on older foliage giving the trees a tufted appearance; they will also feed on current year needles when the older needles are entirely consumed.
- Consecutive years of severe defoliation (more than 70%) will cause growth loss and reduced vigour, which may lead to whole tree mortality.
- Severely defoliated red pine is susceptible to attack by secondary insects (e.g. bark beetles) and Armillaria root rot (Armillaria mellea); if complete defoliation occurs to old and current year foliage, whole tree mortality can occur in one to two years.
Natural controls include parasitic insects, birds and rodent predators. On young open-grown ornamentals, larvae can be removed by hand and destroyed. In addition, a chemical insecticide can be applied to protect larger trees.