Dendrocerus carpenteri（Curtis）and Asaphes suspensus（Nees）are common aphid hyperparasitoids that attack braconid parasitoids in mummified aphids. In this study, we investigated the host discrimination behavior of D. carpenteri in hosts parasitized by each of these hyperparasitoid species, and compared the behavioral process and chemical characteristics of host marks involved in host discrimination. Females of D. carpenteri significantly avoided host mummies parasitized by D. carpenteri and A. suspensus. The avoidance behavior was observed soon after antennal drumming（tapping on the mummy surface）in cases of host mummies parasitized either by D. carpenteri or A. suspensus. This demonstrates that chemical markers deposited on the mummy surface are important cues for host discrimination, regardless of the hyperparasitoid species. Methanol extracts of mummy cases separated from hosts previously oviposited by D. carpenteri induced oviposition avoidance behavior, while methanol and hexane extracts for markers deposited by A. suspensus were active. The adaptive role of the markers in mediating host discrimination by the two hyperparasitoid species and implications for possible use of the semiochemicals involved in future biological control programs are discussed.
The whitefly Bemisia tabaci （Gennadius） is an important economic pest, being a vector of Tomato yellow leaf curl virus （TYLCV）. In this study, we evaluated the inhibitory effect of two insecticides on TYLCV transmission by whiteflies. Tomato plants pretreated with pyrifluquinazon or dinotefuran （0 and 7 days before inoculation） were significantly less infected with TYLCV than untreated plants, while plants pretreated 14 day before inoculation did not show any difference. In contrast, the survival rates of viruliferous whitefly on pretreated plants 0, 7, 14 days before inoculation were significantly lower than those on untreated plants. These results indicate that sprays of these insecticides at 7-day intervals were effective in inhibiting the incidence of TYLCV transmission by whiteflies.
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