Simulated acid rain and the susceptibility of the European pine sawfly (Neodiprion sertifer) larvae to nuclear polyhedrosis virus

Abstract

Little attention has been paid to the effects of pollutants via natural enemies of herbivores, and the effects on interactions among tritrophic levels (host plants - herbivores - natural enemies) have been almost totally neglected. However, the experiment by Neuvonen et al. (1990) suggested that simulated acid rain (SAR) with pH 3 applied to host trees (Scots pine, Pinus sylvestris L.) might reduce the susceptibility of young (first and second instar) European pine sawfly (Neodiprion sertifer (Fourcroy)) larvae to a nuclear polyhedrosis virus (NsNPV). On the other hand, there were no significant effects of SAR with pH 4 on the efficacy of NsNPV, and the effect of SAR was only on the timing of mortality of the larvae reared on pH 3 treated trees: all the larvae died toward the end of the larval period. These results were obtained after the host trees had been treated with SAR for only two growing seasons, which may be insufficient for the expression of many processes.