Hyperparasitism and seasonal patterns of parasitism as potential causes of low top-down control in Euproctis chrysorrhoea L. (Lymantriidae)

Pest suppression is an important ecosystem service provided by biodiversity, though antagonistic interactions may jeopardize its impact on pest suppression. Hyperparasitoids may release herbivore populations from natural enemy pressure and lead to outbreaks directly due to parasitism as well as indirect through behavioural interference. In a previous study we reported that in native populations of Euproctis chrysorrhoea L. (Lymantriidae) primary parasitism was very low and outbreaks were more likely in coastal habitats than inland. Here we hypothesise that hyperparasitoids are the underlying cause of such patterns by reporting data on direct hyperparasitism rates as well as seasonal patterns of parasitoid attack. Of the 17 primary parasitoids attacking E. chrysorrhoea, three were found to be hyperparasitized. Hyperparasitoids attack the most important E. chrysorrhoea primary parasitoids which may explain the pattern of moth density in some habitats. Seasonal patterns of parasitoids attack and flight also help to understand antagonistic interactions among E. chrysorrhoea parasitoids. We discuss the implications of our work in the context of pest control in diverse ecosystems.

Highlights► Browntail moth hyperparasitoids attack three out of the 17 primary parasitoids of this moth. ► The attacked primary parasitoids are among the most important ones. ► Seasonal patterns of parasitoid attack and flight help to understand browntail moth parasitism. ► Hyperparasitism may explain browntail moth densities in certain habitats. ► This study has implications for pest control in diverse forests.