NUCLEAR POLYHEDROSIS-VIRUS TREATMENT EFFECT ON REPRODUCTIVE POTENTIALOF WESTERN TENT CATERPILLAR (LEPIDOPTERA, LASIOCAMPIDAE)

Western tent caterpillar, Malacosoma californicum pluviale (Dyar), lar vae were treated with nuclear polyhedrosis virus (NPV) in the laborato ry to assess whether the presence of virus could potentially explain r educed fecundity observed in declining field populations of the host, In 1992, male and female pupal weights and female fecundity were reduc ed in survivors of virus treatment. In 1993, using the same viral dosa ge on individuals from a different population resulted in reduced pupa l weight (and fecundity) in females only. Strong family effects were a lso detected for male and female pupal weights and fecundity in both y ears. Results from 1992 data showed a significant effect of virus trea tment on fecundity when variability related to pupal weight was remove d, suggesting that NPV could directly affect egg production. This patt ern was not observed in 1993. These experiments suggest that NPV has t he potential to cause reduced fecundity in field populations of the we stern tent caterpillar.