A Japanese isolate of Mamestra brassicae nucleopolyhedrovirus (MabrNPV) was identified phylogenetically as a group II nucleopolyhedrovirus (NPV) that is related closely to other NPVs isolated from Mamestra spp. based on nucleotide sequence data of its polh, egt and lef-3 genes. The multiplication of MabrNPV in M. brassicae larvae was characterized following inoculation at various doses and in combination with the fluorescent brightener Tinopal by measuring temporal changes in the concentrations of its viral DNA using real-time quantitative PCR. The growth curves of budded-virus replication were analysed by fitting the data of viral DNA concentration in the host haemolymph to a modified Gompertz model. When fifth-instar larvae were inoculated with an LD 95 equivalent dose of MabrNPV and Tinopal, the time lag between the onset of primary and secondary infection was estimated to be 25 h. Another 65 h was required to reach a plateau titre equivalent to a level of 10 9 virions ml "1 in the haemolymph. All larvae died during the sixth instar following this inoculation regime. In contrast, following inoculation with a 1000-fold higher dose of MabrNPV and Tinopal, the time lag between the onset of primary and secondary infection was only 20 h. Subsequently, the same plateau titre was reached after a further 20 h. Following this inoculation regime, most larvae died during the fifth instar. Quantification of viral DNA by real-time quantitative PCR and application of the Gompertz model are valuable for the characterization of baculovirus replication in vivo.

The synergistic enhancement of nucleopolyhedrovirus (NPV) infection by granuloviruses (GVs) is well documented; and a GV granule protein, named viral enhancin, has been identified as an active contributor to this effect. We detected the presence of two proteins with molecular mass of 93 and 108 kDa in granules of a GV isolated from Xestia c-nigrum (L.) (XecnGV) as candidates for enhancin, and we confirmed that at least the 108-kDa protein enhances the infectivity of Mamestra brassicae nucleopolyhedrovirus (MabrNPV). We tested the effect of virion-free proteins obtained from XecnGV granules (GVPs) on MabrNPV infection, and we made a comparison with an enhancing chemical, the stilbene-derived fluorescent brightener Tinopal. Bioassay was performed employing the diet contamination method, by using second instars of Mamestra brassicae (L.) (Lepidoptera: Noctuidae). The enhancing effects of GVPs (0.1 mg/g diet) and Tinopal (1 mg/g diet) were estimated to be 70.7-81.5-fold and 26.9-33.7-fold, respectively, as calculated from the LC50 values of MabrNPV with or without the additives. The additives reduced the lethal time of MabrNPV-infected larvae and they caused death at a younger instar. These results suggest that GVPs can enhance MabrNPV infection as effectively as Tinopal.

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The influence of food supply on the parasitoid Cotesia plutellae regarding the survival and reproductive potential of a non-target pest, pea leafminer Chromatomyia horticola, was examined in the laboratory. The male longevity of the leafminer dramatically increased when sugar or honey was available. On the other hand, sugar-or honey-fed females lived shorter lives than those fed on the host plant. Lifetime copulation times of the males were increased by their food supply. The lifetime fecundity of a pair significantly increased sugar or honey was supplied. This phenomenon was mainly explained by the positive relationship between the fecundity and the copulation count of females. We discuss the risk of an additional food supply increasing the numbers of non-target pests.

Nested PCR amplification of a Spodoptera litura nucleopolyhedrovirus (SpltNPV) lef-8 gene fragment was performed on egg masses and larvae of S. litura, and resulted in detection of a latent SpltNPV in 20.0% of "healthy" laboratory stock samples, and in 22.6% of samples collected at different periods and in remote places in Kagoshima Prefecture. The PCR product sequences showed 99% similarity to the published lef-8 sequence of SpltNPV, confirming that the amplification products were derived from SpltNPV. Further, cross-inoculation of laboratory stock S. litura larvae with Mythimna separata NPV (MyseNPV) activated the latent virus, which provoked a change in the virulence of MyseNPV samples collected from cadavers of S. litura. Our data suggest that caution should be taken when using S. litura as a host to produce heterologous NPVs.

We compared the infectivity of two nucleopolyhedroviruses (NPVs), MyseNPV G isolated from Mythimna separata (Walker) (Lepidoptera: Noctuidae) and SpltNPV S isolated from Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). MyseNPV G was more pathogenic against M. separata than against S. litura. Although SpltNPV S was more pathogenic than MyseNPV G against S. litura, it did not infect M. separata. Restriction endonuclease (REN) analysis of viral genomic DNA revealed that the two NPVs have quite different REN profiles. Based on nucleotide sequences of the coding regions of polyhedrin, lef-8 and lef-9, SpltNPV S was closely related to other SpltNPV isolates, whereas MyseNPV G appeared to belong to the Mamestra NPV group, and was distinct from a Chinese isolate of Leucania (=Mythimna) separata NPV. The potential of MyseNPV G and SpltNPV S to control pest insects is discussed.

The insecticidal activity of Beauveria bassiana GHA derived from a commercial mycoinsecticide BotaniGard ES against Frankliniella occidentalis was determined in a bioassay by dipping the female adults into a conidial suspension. The 90% lethal concentration of B. bassiana GHA was estimated to be 9.7 9 10 6 conidia/ml. The lethal times for achieving 90% mortality of thrips inoculated with a 1/500-diluted solution of BotaniGard ES and a 10 7.5 (3.16 9 10 7 ) conidia/ml suspension of B. bassiana GHA were estimated to be five and six days, respectively. When the treated thrips were exposed to a high relative humidity (RH) of over 99% for various periods and then transferred to 60% RH, the requisite lengths of the high-humidity period to achieve 90% mortality of the thrips at six days after inoculation were estimated to be 46 and 47 h in BotaniGard ES and B. bassiana GHA, respectively. Fungal multiplication in the thrips was detected between 48 to 60 h after inoculation by measuring Beauveria-specific DNA in the host following inoculation with a B. bassiana GHA suspension of 10 7.5 conidia/ml using a real-time quantitative PCR. The mycelial growth in the host hemocoel was not influenced by the low-humidity condition.

Although it is well known that the application of broad‐spectrum synthetic insecticides reduces the effectiveness of natural enemies, the details of the actual mechanisms, including the lethal and sublethal effects of this reduction, are not fully understood. The inhibitory effects of a pyrethroid insecticide (permethrin), Adion 20% EC on the flight responses, host‐searching behaviour and foraging behaviour of Cotesia vestalis (Hymenoptera: Braconidae), a larval parasitoid of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), were investigated under laboratory conditions. In choice trials, the wasps showed significant preference for P. xylostella‐infested Komatsuna plants over insecticide‐treated plants, suggesting an inhibitory effect of the insecticide on the flight response of C. vestalis. When offered a pair of plants, the wasps showed a significant preference for P. xylostella‐infested plants compared to uninfested plants. However, significantly more wasps were attracted to infested permethrin‐treated plants than to uninfested plants, suggesting that the wasps are attracted to the volatile infochemicals from the infested plants, even if treated with permethrin. The searching time was significantly shorter and the mortality of C. vestalis adults on the insecticide‐treated plants significantly higher than in the control plants treated with distilled water. These results suggest that the application of the insecticide had an inhibitory effect on the wasps’‐searching behaviour and consequently reduced the effectiveness of C. vestalis as a biological control agent against P. xylostella. In addition, the strength of the inhibitory effect of permethrin on the attraction of the wasps to the plants is critical to the survival of C. vestalis. Our results suggest that the attraction of the wasps to the permethrin‐treated infested plants increases the risk of their exposure to this insecticide.