Sublethal nucleopolyhedrovirus infection effects on female pupal weight, egg mass size, and vertical transmission in gypsy moth (Lepidoptera : Lymantriidae)

Gypsy moth females that survived inoculation with Lymantria dispar (L.) nuc leopolyhedrovirus (LdNPV) as fifth instars were smaller as pupae and laid f ewer eggs as adults. Treatment with both wild type virus containing the egt gene and a genetically manipulated, egt- virus, lacking this gene, reduced pupal mass to a similar degree. Sublethal infection with wild type virus r educed the masses of surviving pupae at 20, 25, and 28 degreesC. A relation ship between virus dose (5,000, 50,000 and 500,000 occlusion bodies per lar va), mass of pupae, and egg mass size only occurred in one experiment in wh ich larvae were reared at 25 degreesC and inoculated 5 d after molt to the fifth instar. Vertical transmission of overt infection occurred in two of 1 3 egg masses (15%) produced by females inoculated with virus as larvae. The five larvae infected with virus were approximate to0.5% of the larvae test ed. Whether sublethal effects of LdNPV infection occur in field populations of gypsy moth remains to be tested.