Behavioural observations in both no-choice and choice tests provide reassurance against the outliers that invariably occur within host range testing
Withers, TM and Allen, GR and Todoroki, CL and Pugh, AR and Gresham, BA, Behavioural observations in both no-choice and choice tests provide reassurance against the outliers that invariably occur within host range testing, 9-13 September, Perugia, Italy (2019) [Conference Edited]
The solitary larval endoparasitoid Eadya daenerys (Hym.: Braconidae) is a new biocontrol agent of Paropsis charybdis (Col.: Chrysomelidae: Chrysomelinae), a eucalypt pest in New Zealand. The oviposition behaviour of females parasitoids was examined to compare two assay types and improve the ecological host range prediction of the parasitoid. No-choice sequential and two-choice behavioural observations were undertaken against nine species of non-target beetle larvae that included a native beetle, introduced weed biological control agents, and invasive pest species. Over both assay types ovipositor insertions occurred rarely in all non-target species sitting on a sprig of their target foliage. On-plant attack rates (no. ovipositor insertions / total time on that host’s plant) were significantly lower for non-targets (mean 0 – 1.6 attacks/min) compared to target P. charybdis larvae (mean 1.1 – 4.4 attacks/min). In sequential no-choice assays the order of first presentation (A-B vs B-A) had no significant effect on the median number of ovipositor insertions, or the attack rate on the plant, with beetle species being far more important in determining the end result. The median number of larval ovipositor insertions was always higher towards target larvae than non-target larvae, but in one case it was not significantly different. Two outliers (one statistically significant, one not), when individual E. daenerys did multiple attacks against non-target larvae in two-choice assays, were suggestive of a central excitatory state in the presence of the target. Rejecting or disregarding non-target larvae upon contact was another behaviour expressed by E. daenerys, leading us to conclude the outlier attacks were probably not reflecting normal host selection behaviour. No behavioural measure was significantly different between no-choice and two-choice tests. The observations revealed that when E. daenerys was in contact with non-target plants bearing non-target larvae they tended to rest or groom. Behavioural results were consistent with field host relationship studies in the country of origin (Australia), and in combination with physiological host range data, indicate that E. daenerys is highly unlikely to attack any species apart from pest paropsines feeding on Eucalyptus.