Synergism of teflubenzuron and chlorfluazuron in an acylurea‐resistant field strain ofPlutella xylostellaL. (lepidoptera: Yponomeutidae)

摘要

AbstractTopical application of the synergists piperonyl butoxide (PB) andS,S,S‐tributyl phosphorotrithioate (DEF) to second‐instar larvae of a standard laboratory strain (FS) and an unselected Malaysian field strain (CH) of the diamondback mothPlutella xylostellahad no significant effect on the toxicity of the acylurea insecticides, chlorfluazuron and teflubenzuron, in a subsequent leafdip bioassay. In contrast, pre‐treatment with PB or DEF in acylurea‐selected subpopulations of the CH strain with varying levels of cross‐resistance to chlorfluazuron and teflubenzuron significantly increased (up to 34‐fold and 28‐fold, respectively) the toxicity of both compounds, suggesting that microsomal monooxygenases and esterases may be involved in resistance. The addition of a mineral oil, ‘Sunspray 6E’, to topically‐applied chlorfluazuron consistently reduced its LD50value, and the effect of the oil appeared to be greatest on the most resistant population ofP. xylostella.However, the effects of the oil were not significant (P>0·05) and further studies are necessary to determine whether a penetration factor is pres