Effect of the acylurea insect growth regulator teflubenzuron on the endo‐larval stages of the hymenopteran parasitoidsCotesia plutellaeandDiadegma semiclausumin a susceptible and an acylurea‐resistant strain ofPlutella xylostella

摘要

AbstractThe toxicity of the acylurea, teflubenzuron, was assessed against larval stages of the hymenopteran parasitoids,Cotesia plutellaeKurdjumov andDiadegma semiclausumHellén in a susceptible laboratory strain and a teflubenzuron‐resistant field strain of the diamondback moth,Plutella xylostellaL. In fourth‐instar hosts (L4), when both parasitoid species were in their final larval instar, teflubenzuron significantly (P0.05) effect onC. plutellae, although a small proportion of the latter were unable to reproduce. Treatment of L4 hosts with teflubenzuron (>LD50) had no significant (P>0.05) effect on the fecundity of surviving females ofD. semiclausum. Similar differential toxicity with teflubenzuron was observed in L2 hosts, when parasitoids were at the egg or early larval instar stage. There was no apparent increased effect of teflubenzuron on either species of parasitoid when highly resistant (c. 4000‐fold) L2 hosts (field strain) were treated with concentrations of teflubenzuron two to three orders of magnitude greater than in equivalent experiments with the susceptible host strain. This suggests that host resistance to teflubenzuron confers some protection to both species of parasitoid. Uptake experiments with [14C]teflubenzuron showed that accumulation of radioactivity was much greater inD. semiclausumthan inC. plutellaeand this may account for the differential toxicity observed. The results are discussed in relation to the field status of these parasitoid species. The influence of insecticide resistance in the host on endo‐larval parasitoids is also co