Host testing of the parasitoid Cotesia urabae (Austin & Allen, 1989) (Hymenoptera: Braconidae) to assess the risk posed to the New Zealand nolid moth Celama parvitis (Howes, 1917) (Lepidoptera: Nolidae): do host deprivation and experience influence accept

Abstract

Retrospective host specificity testing of the recently introduced biological control agent Cotesia urabae Austin & Allen, 1989 against Uraba lugens Walker, 1863 was conducted to assess the potential risk posed to the endemic nolid moth Celama parvitis Howes, 1917. The effect that different periods of host deprivation and prior host exposure (‘experience’) had on the parasitoid's readiness to attack a non-target species was examined in a sequence of consecutive no-choice tests. Even though C. urabae was observed to oviposit on C. parvitis in 91% of the no-choice tests, no parasitoids emerged from the 52% of larvae that survived to complete larval development. Host larvae that died during the laboratory rearing were dissected revealing that 63% contained a parasitoid larva, none of which had developed beyond the second instar within the larvae of C. parvitis. These results show a high level of developmental failure of C. urabae within C. parvitis, confirming that it is not a suitable physiological host. Therefore, potential negative impacts of C. urabae on C. parvitis in the wild are likely to be negligible. Significant differences were found in the attack times between parasitoids with different levels of host deprivation, with younger parasitoids taking longer to initiate attack behaviour. Also, it was observed that the lag until first attack decreased significantly after previous experience with the same host in a succession of no-choice tests. These results suggest that host deprivation and experience may play an important role in increasing the responsiveness to non-target species by C. urabae.