Bait (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.
Hymenopteran, parasitoid wasps have good potential for use in integrated pest management (IPM); for example, the gregarious ectoparasitoid, Eulophus pennicornis, has been suggested as a biological control agent for larvae of the tomato moth (Lacanobia oleracea L.). However, the processes by which such parasitic larvae are able to utilize the nutritional resource provided by the host have been little studied. Protease activity was present in E. pennicornis larvae, and characterization of the enzymes responsible for proteolysis was performed using a range of synthetic substrates and specific inhibitors. Serine protease enzymes was both trypsin- and chymotrypsin-like activities were present. A range of plant-derived serine protease inhibitors was tested for activity against these enzymes. Certain inhibitors, notably soybean Kunitz inhibitor (SKTI), inhibited enzyme activity by > 80% at < 10(-5) M. When SKTI was fed to L. oleracea larvae in an artificial diet, the inhibitor was subsequently detected within the larval haemolymph, showing that protease inhibitors in the host diet can be delivered to a parasitoid via the host haemolymph. If transgenic plants expressing foreign protease inhibitors for protection against insect pests are to form a component of IPM systems, possible adverse effects, whether direct or indirect, of transgene expression on parasitoids like E. pennicornis should be considered.
Serum from larvae of Lacanobia oleracea L. (Lepidoptera; Noctuidae) parasitized by Eulophus pennicornis (Hymenoptera; Eulophidae) and from normal non‐parasitized larvae is capable of agglutinating rabbit, sheep, calf, goat, chicken, horse and human erythrocytes, but not yeast. Studies with a range of inhibitory carbohydrates showed that serum lectins(s) had specificity for sugars containing galactose and for rhamnose, and for the glycosubstances fetuin and asialofetuin. Lectin activity is heat‐labile and is not dependent on calcium. Parasitism by E. pennicornis caused an increase in the agglutination titre of the serum from larvae of L. oleracea but not an increase in specific activity (titre per mg protein per ml). However, when venom from the venom gland of female wasps was injected into L. oleracea larvae, both the agglutinating activity and the specific activity of the larval serum increased. The possible causes of this increase are discussed. It is suggested that venom contains antigenic components which, when injected into the haemocoel of the L. oleracea larva, may be increasing lectin synthesis and/or release into the serum.
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