Why introducing a parasitoid of Paropsis charybdis Stål, 1860 (Coleoptera: Chrysomelidae) larvae is expected to enhance biological control of this Eucalyptus pest in New Zealand

Abstract

Paropsis charybdis (Coleoptera: Chrysomelidae) has been a major pest of Eucalyptus spp. since invading New Zealand from Australia over 100 years ago. Here, we report on the phenology, egg parasitism and defoliation levels of P. charybdis at two Eucalyptus nitens plantations in the central North Island of New Zealand and assess the establishment prospects and potential impact of a new biological control agent, the larval parasitoid Eadya daenerys. Field monitoring found that 90–100% of first generation P. charybdis eggs emerged, showing that the existing egg parasitoids Enoggera nassaui (Hymenoptera: Braconidae) and Neopolycystus insectifurax (Hymenoptera: Pteromalidae) are ineffective at controlling this generation. Further field monitoring revealed effective control of second generation eggs by E. nassaui and N. insectifurax despite the presence of Baeoanusia albifunicle (Hymenoptera: Encyrtidae), a hyperparasitoid of E. nassaui. Phenology data show that first generation P. charybdis larvae will likely be synchronous with the adult emergence of E. daenerys (Hymenoptera: Braconidae) the new larval endoparasitoid proposed to be introduced from Australia. Climate matching predicts E. daenerys could establish in all areas of New Zealand where P. charybdisimpacted Eucalyptus spp. plantations are grown. The addition of a larval endoparasitoid could significantly contribute to the suppression of P. charybdis by decreasing first generation larval survival.

Comparison of the biology, ecology and potential pest impacts of the eucalypt-defoliating leaf beetles <i>Paropsisterna cloelia</i> and <i>Paropsis charybdis</i> (Coleoptera: Chrysomelidae) in New Zealand

“…Neopolycystus insectifurax has not been confirmed in Southland to date despite 1600 individuals being released there in 2003/04 (T. Withers, personal communication). The results of these field studies demonstrated the need for additional biological control agents to target the spring generation of P. charybdis (Pugh et al 2020).…”

“…On P. charybdis, both species readily parasitise 100% of eggs supplied to them in laboratory trials (Bain & Kay 1989) and are regularly reared from field-collected eggs (Berry 2003;Jones & Withers 2003;Mansfield et al 2011;Murphy 2002). Although the two parasitoids reach high parasitism levels above 80% of the second late-summer generation of P. charybdis eggs in the North Island, they are generally not able to control the first appearance of the spring generation of the beetle (parasitism <20% prior to December) (Jones & Withers 2003;Mansfield et al 2011;Murphy & Kay 2000;Pugh et al 2020). Enoggera nassaui has also been reared from Pst.…”

“…At mid-season (December), B. albifunicle was overtaking E. nassaui and by late season, parasitism and emergence of E. nassaui were reduced to zero by the hyperparasitoid. Overall, late-season parasitism rates are high and dominated by N. insectifurax (Jones & Withers 2003;Mansfield et al 2011;Pugh et al 2020). While N. insectifurax does compensate for the reduced E. nassaui populations caused by the hyperparasitoid B. albifunicle (Mansfield et al 2011), it is not present in all eucalypt growing areas.…”

Circadian and seasonal flight activity differences between the sexes of the biocontrol agent Eadya daenerys (Hymenoptera: Braconidae) and the impact of host size on adult emergence

“…In Tasmania, E. daenerys is most commonly reared from Paropsisterna agricola Chapius and to a lesser extent P. charybdis (Peixoto et al 2018). It is active for a very short time window after emerging from the soil where it has spent around 10 months as a pupa having exited its host's prepupal stage (Pugh et al 2020). Other minor hosts of E. daenerys include Paropsisterna bimaculata Olivier and Paropsisterna nobilitata Erichson (Peixoto et al 2018).…”

“…Other minor hosts of E. daenerys include Paropsisterna bimaculata Olivier and Paropsisterna nobilitata Erichson (Peixoto et al 2018). Because no other recorded hosts are present in New Zealand, E. daenerys will utilise the larger P. charybdis as its primary host (Pugh et al 2020). In New Zealand, P. charybdis undergoes two generations each year (Withers & Peters 2017), but it is essential for this biological control program to be effective that the parasitoid flight season overlaps with the first generation of the target as has been predicted (Pugh et al 2020).…”