부산대학교 도서관

In this paper we report on the effect of host plant variation on the susceptibility ofHelicoverpa zeaandHeliothis virescenslarvae to theHelicoverpa zeanucleopolyhedrovirus (HzNPV). LarvalH. zeaandH. virescenstreated with HzNPV on foliage from various hosts showed thatH. virescenswere significantly more susceptible to HzNPV on cotton and Carolina geranium thanH. zea,whereasH. zeawere significantly more susceptible to HzNPV on velvetleaf thanH. virescens.Plant phenology had an effect on larval susceptibility to HzNPV. Vegetative or reproductive tissues of cotton, soybean, tomato, crimson clover, Carolina geranium, and velvetleaf were treated with HzNPV and fed to second-instarH. zeaorH. virescens.Host phenology significantly affected the mortality of HzNPV-treatedH. zeaon all hosts except tomato. HzNPV-treatedH. zeafed on vegetative tissues of crimson clover, Carolina geranium, velvetleaf, and soybean had significantly higher mortality than those fed on reproductive tissues. On the contrary, larval susceptibility to HzNPV on cotton was greater on reproductive than vegetative tissues.H. virescenssusceptibility to HzNPV was greater on vegetative than reproductive tissue for crimson clover. In addition, we examined the effect of prior herbivory on larval susceptibility to the HzNPV. Cotton, soybean, tomato, and velvetleaf plants were either untreated or wounded with three fourth-instarH. zeaorH. virescens.Neonates were reared on the respective treatments and then treated with HzNPV as second instars. Non-HzNPV-treatedH. zealarvae fed on wounded foliage had up to 93.1% reduced weight gain compared with those fed on unwounded foliage. The weight reduction was greatest on cotton (93.1%), followed by velvetleaf (80.6%), tomato (78.4%), and soybean (54.1%). Prior herbivory on all plants significantly affected the larval growth of nontreatedH. zea.In nontreatedH. virescens,the reduction in weight was greatest on velvetleaf (63.1%), followed by soybean (29.2%) and cotton (21.8%). However, the effect of prior herbivory on cotton did not significantly affect the larval growth of nontreatedH. virescens.Only virus-treatedH. zeathat fed on wounded virus-treated tomato foliage showed significantly enhanced larval mortality (47.7%) compared with larvae on unwounded foliage. For HzNPV-treatedH. virescens,only prior herbivory on cotton significantly enhanced larval mortality (39.4%).