Observations of parasitoid behaviour in both no‐choice and choice tests are consistent with proposed ecological host range

Abstract

The solitary larval endoparasitoid Eadya daenerys Ridenbaugh (Hymenoptera: Braconidae) is a proposed biocontrol agent of Paropsis charybdis St al (Coleoptera: Chrysomelidae, Chrysomelinae), a pest of eucalypts in New Zealand. Eadya daenerys oviposition behaviour was examined in two assay types during host range testing, with the aim of improving ecological host range prediction. No-choice sequential and two-choice behavioural observations were undertaken against nine closely related species of New Zealand non-target beetle larvae, including a native beetle, introduced weed biocontrol agents, and invasive paropsine beetles. No behavioural measure was significantly different between nochoice and two-choice tests. In sequential no-choice assays the order of first presentation (target-nontarget) had no significant effect on the median number of attacks or the attack rate while on the plant. Beetle species was the most important factor. Parasitoids expressed significantly lower on-plant attack rates against non-targets compared to target P. charybdis larvae. The median number of attacks was always higher towards target larvae than towards non-target larvae, except for the phylogenetically closest related non-target Trachymela sloanei (Blackburn) (Coleoptera: Chrysomelidae, Chrysomelinae). Most non-target larvae were disregarded upon contact, which suggests that the infrequent attack behaviour observed by two individual E. daenerys against Allocharis nr. tarsalis larvae in two-choice tests and the frass of Chrysolina abchasica (Weise) was probably abnormal host selection behaviour. Results indicate that E. daenerys is unlikely to attack non-target species apart from Eucalyptus-feeding invasive paropsines (Chrysomelinae). Non-lethal negative impacts upon less preferred non-target larvae are possible if E. daenerys does attack them in the field; however, this is likely to be rare.

Plant Phytochemistry Influences the Niche Breadth of Oligophagous Parasitoids (Hymenoptera: Braconidae)

“…Eucalyptusplantations in New Zealand, with E. daenerys approved to controlP. charybdis Stål, 1860 (T. M. Withers, Allen, Todoroki, Pugh, & Gresham, 2020) and E. annleckieae Ridenbaugh, 2018 as a potential agent to control Paropsisterna (=Pst. variicollis(Chapuis) in Peixoto et al, 2018) (Nahrung et al, 2020).…”

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

“…E. daenerys is a univoltine larval koinobiont endoparasitoid approved in 2019 for release as a biological control agent against the invasive leaf beetle Paropsis charybdis Stål in New Zealand (Withers et al 2021). E. daenerys is one of the several Australian species of Eadya that are larval endoparasitoids of eucalypt-feeding chrysomelids (Peixoto et al 2018).…”

“…agricola, so we aim to explore the relationship between host size and parasitoid development. The host size relationship for E. daenerys development is important as it has already been used to interpret the results of nontarget host specificity testing conducted on non-target species of chrysomelid beetles of varying sizes in New Zealand (Withers et al 2020(Withers et al , 2021.…”

Entomophagous insects – an introduction

“…In the work presented by Withers et al (2021), parasitoid behavior is used as a tool to evaluate the ecological host range of Eadya daenerys Ridenbaugh (Hymenoptera: Braconidae), a candidate biological control agent of the invasive eucalyptus pest Paropsis charybdis Stål (Coleoptera: Chrysomelidae, Chrysomelinae) in New Zealand. Herbivore larvae were tested on eucalyptus plants, hence with cues from both hosts and their host plant, and the parasitoid response was evaluated towards larvae of nine closely related species – including a native species, invasive species, and introduced weed biocontrol agents.…”