Techniques for Measuring Early-Larval Dispersal of Spruce and Jack Pine Budworms
- Jennings, Daniel T.
US Forest Service
- Fellin, David G.
- Batzer, Harold O.
- Housewart, Mark W.
- Beckwith, Roy C.
Early-instar larvae of the spruce budworm, Choristoneura Jumiferana (Clem.); the western spruce budworm, C. occidentalis Freeman; and the jack pine budworm, C. pinus pinus Freeman, disperse periodically within and from their host trees. Some larvae disperse by crawling, but most dispersal occurs when the small larvae ''spin down" from trees on silken thread . The larvae spin silk from gland. located near their mouth parts. The silk threads are anchored to branches or other attachment site, and the larvae continue to spin silk as they descend from the tree. Frequently, the threads break at their points of attachment and larvae are carried by winds, sometimes for great distances. The purpose of this paper is to describe techniques developed for measuring early-larval dispersal of spruce and jack pine budworms.
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