Exploring the fourth trophic level: Do hyperparasitoids influence biocontrol of a forestry pest in a native system?

Abstract

The accidental introduction of an obligate egg hyperparasitoid, Baeoanusia albifunicle, reduced the effectiveness of the deliberately introduced Enoggera nassaui as a biological control agent of Paropsis charybdis in eucalypt forestry in New Zealand. Baeoanusia albifunicle also hyperparasitises the only primary egg parasitoid associated with P. atomaria in South-East Queensland (SEQ) eucalypt forestry in Australia. We investigated the hyperparasitoid complex associated with Neopolycystus sp. in SEQ, recording relative species abundance, phenology and sex ratios at three fi eld sites across two seasons. Overall, 27% of Neopolycystus sp. were hyperparasitised. Relative wasp abundance was consistent between sites and seasons, with the primary parasitoid the most common emergent (74%) from parasitised P. atomaria eggs, followed by B. albifunicle (18%), while the obligate hyperparasitoids Aphaneromella sp. and Neblatticida sp. each represented less than 5% of wasps. No relationship between primary parasitoid availability and hyperparasitism rates was apparent, nor was there evidence of hyperparasitism reducing Neopolycystus sp. impact on P. atomaria.