Roland, J. 1994. After the decline: what maintains low winter moth density after successful biological control?
Journal of Animal Ecology 63:392-398.
Abstract
- Life-table data for winter moth are analysed for an 8-year period following introduction of parasitoids for
biological control in British Columbia, Canada.
- Winter moth density declined in 1984, and has remained low since 1985 at an average density of approximately
1.2 adults per m squared.
- Introduced parasitoids contributed to mortality during the decline, and have a weak, delayed density-dependent
effect at the new low density.
- Mortality of unparasitized pupae in the soil (primarily by predation) is strongly, and directly density-dependent
at the new low density, and is the factor which is most strongly regulatory.
- Analysis indicates that the strong regulation of winter moth numbers by generalist predators allows parasitism
levels to vary greatly after suppression without the eruption of winter moth populations; if parasitism were absent, winter moth
populations would erupt to pre-biocontrol levels.
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