Comparative effects of selected natural insecticides on Heliothis virescens (Lepidoptera: Noctuidae) larvae
1994
Yoshida, H.A. | Toscano, N.C.
Diet-incorporation bioassays were conducted to evaluate effects of selected natural insecticides on the tobacco budworm, Heliothis virescens (F.). Compounds evaluated were azadirachtin, kryocide, pyrethrum, rotenone, ryania, and sabadilla. Survivorship within the rotenone (87.3%) treatment was not significantly different from that in the control (83.3%); larvae exposed to ryania and azadirachtin rarely survived beyond the first stadium. Survivorship among the kryocide, pyretbrum, and sabadilla treatments was 56.7, 40.0, and 35.0%, respectively. With the exception of rotenone, developmental time was significantly longer for all treatments compared with the control. Larvae maintained on the pyrethrum diet required approximately 20 additional days to reach the pupal stage. Similarly, development among larvae reared on kryocide and sabadilla was lengthened approximately 9 and 13 d, respectively. Ensuing pupal weight within the pyrethrum, kryocide, and sabadilla treatments were also significantly lower. Significant differences in the consumption and utilization of food by fourth instars also were found among the treatments. In general, relative consumption and growth rates, as well as utilization efficiencies, were significantly lower among larvae confined to the sabadilla, azadirachtin, kryocide, and ryania treatments.
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