Pine false webworm

Distribution

Alberta, Newfoundland and Labrador, Ontario, Quebec.

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)

Needle, Soil

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.

Comments

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.

References

Drooz, A.T., editor. 1985. Insects of eastern forests. U.S. Dept. Agric., For. Serv., Washington, D.C. Misc. Publ. 1426, 608 p.

Lyons, D.B. 1995. Pamphile à tête rouge (Acantholyda erythrocephala), pp. 245-251, in J. A. Armstrong et W.G.H. Ives (réd.). Insectes forestiers ravageurs au Canada. Ressour. nat. Can., Serv. can. for., Ottawa (Ont.).

Lyons, D.B.; G.C. Jones, 1998. What do we know about the biology of the pine false webworm in Ontario? in Proceedings of a Workshop on the Pine False Webworm. On. Minist. Nat. Ressour.. and the Fac. For., Univ. Toronto. Toronto, ON. 49 p.

Howse, G.M. 1998. The history, distribution and damage levels of the pine false webworm in Canada. in Proceedings of a Workshop on the Pine False Webworm. On. Minist. Nat. Ressour.. and the Fac. For., Univ. Toronto. Toronto, ON. 49 p.

Helson, B.V.; D.B. Lyons, 1998. Chemical and biorational control of the pine false webworm. in Proceedings of a Workshop on the Pine False Webworm. On. Minist. Nat. Ressour. and the Fac. For., Univ. Toronto. Toronto, ON. 49 p.

Rose, A.H.; Lindquist, O.H.; Nystrom, K.L. 1999. Édition révisée. Insectes des pins de l’est du Canada. Ressour. nat. Can., Serv. can. for., Sault Ste. Marie (Ont.). Publ. 1313F. 128 p.

Main Host(s)

Austrian pine, Japanese red pine, jack pine, lodgepole pine, mugho pine, ponderosa pine, red pine, whitebark pine