Aspen Bibliography

Budbreak phenology and natural enemies mediate survival of first-instar forest tent caterpillar (Lepidoptera: Lasiocampidae)

Document Type

Article

Journal/Book Title/Conference

Environmental Entomology

Volume

27

Issue

3

First Page

1368

Last Page

1374

Publication Date

1999

Abstract

Synchrony of egg hatch with budbreak has been proposed as an important component in the population dynamics of many spring feeding forest Lepidoptera. Here, we examine the consequences of phenological asynchrony with the budbreak of trembling aspen ( Populus tremuloides Michaux) for cohorts of forest tent caterpillar, Malacosoma disstria Hübner, larvae in north central Alberta, Canada. The timing of eclosure was adjusted through temperature exposure in the laboratory so that pairs of hatching egg bands were placed on trees belonging to a single aspen clone at intervals beginning 2 d before and at 2, 6, 10, and 18 d after budbreak. On each tree, 1 egg band was protected from predation with a sleeve cage and the other was left unprotected. Larvae from later hatching cohorts required significantly more calendar days and nearly 3 times as many degree-days to complete the 1st instar as did those hatching in synchrony with budbreak. Survivorship of later hatching cohorts was reduced drastically by invertebrate predation in unprotected groups but no change in overall survival was recorded for protected groups, suggesting that protracted development times caused by declining foliar quality enhanced the success of natural enemies. We hypothesize that a narrow phenological window in host quality after budbreak and its interaction with natural enemies has exerted strong selective pressure on larvae to emerge from eggs as early as possible in the spring and that this window is a potent force in determining the dynamics of low density populations of tent caterpillars.

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