The effects of the insect growth regulator lufenuron on oriental cockroach, Blatta orientalis, and german cockroach, Blattella germanica, populations in simulated domestic environments

Abstract

AbstractBait (50 mg AI kg−1) and spray (10 mg AI m−2) formulations of the novel insect growth regulator (IGR) lufenuron were tested against populations of the Oriental cockroach Blatta orientalis L. and the German cockroach Blattella germanica L. that had been established in simulated domestic environments. The treated populations of B. germanica declined rapidly three to four months after the start of bait or spray treatment, and were completely eradicated after 12 months. As well as disrupting the moulting process, lufenuron affected the reproduction of B. germanica by preventing the hatch of the oothecae. In B. germanica, it appeared probable that lufenuron was transferred from female cockroaches to the oothecae while they were being carried. By contrast with B. germanica, the treated populations of B. orientalis did not show any substantial decline compared with the control, even after 18 months' exposure to lufenuron bait or spray treatments. Moreover, neither moulting nor reproduction in the populations of B. orientalis appeared to be affected by either of the lufenuron treatments. Subsequently, laboratory investigations with surface deposits of either technical or formulated lufenuron, applied at dose rates up to 50 mg AI m−2, failed to demonstrate any significant effects on the development or reproduction of B. orientalis. Laboratory tests with first‐instar nymphs of both species revealed substantial differences in sensitivity to the moult‐disrupting effects of the compound. These differences extended to the adult insects, where reproduction was markedly affected in B. germanica, but apparently unaffected in B. orientalis. Thus, both bait and spray formulations of lufenuron have been shown to provide rapid and effective control of German cockroach populations in simulated domestic environments. However, the same treatments were much less effective against similar populations of the Oriental cockroach. These results are discussed in terms of the potential effectiveness of lufenuron as a cockroach control agent, and in relation to the substantial differences in susceptibility to the inhibitory effects of this compound on reproduction that were apparent between Blatta orientalis and Blattella germanica.