Non-contact effects of the parasitoid Sclerodermus guani on its two cerambycid host species
摘要
The parasitoid Sclerodermus guani is a biological control agent of wood-boring insect pests. In addition to directly killing hosts through contact, there has been a report that it could also negatively affect hosts via non-contact effects. To verify this, we investigated non-contact effects of S. guani alone or a S. guani-host complex on nearby uncontacted larvae of two cerambycid species, Thyestilla gebleri and Monochamus alternatus. Specifically, in two distance bioassays we determined the effects of visual, olfactory and mechanical vibration of the parasitoid on its host. Results demonstrated that within shorter distance, S. guani induced developmental delays in both M. alternatus and T. gebleri larvae under non-contact conditions. Additionally, the presence of S. guani increased the proportion of T. gebleri larvae that developed abnormally to the adult with disabled wing and appendage. However, no significant effects on cerambycid larvae were observed when the parasitoid was in a longer distance from larvae. Another significant finding is that the parasitic behavior of the S. guani on the cerambycid host did not affect the behavior or development of the adjacent host larva. Therefore, the conclusion can be made that foraging behavior of S. guani is a critical factor contributing to these non-contact effects on host larvae.