COMPARATIVE EFFECTS OF SELECTED NATURAL INSECTICIDES ON HELIOTHIS-VIRESCENS (LEPIDOPTERA, NOCTUIDAE) LARVAE

Diet-incorporation bioassays were conducted to evaluate effects of sel ected natural insecticides on the tobacco budworm, Heliothis virescens (F.). ComPounds evaluated were azadirachtin, kryocide, pyrethrum, rot enone, ryania, and sabadilla. Survivorship within the rotenone (87.3%) treatment was not significantly different from that in the control (8 3.3%); larvae exposed to ryania and azadirachtin rarely survived beyon d the first stadium. Survivorship among the kryocide, pyrethrum, and s abadilla 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 py rethrum diet required almost-equal-to 20 additional days to reach the pupal stage. Similarly, development among larvae reared on kryocide an d sabadilla was lengthened almost-equal-to 9 and 13 d, respectively. E nsuing pupal weight within the pyrethrum, kryocide, and sabadilla trea tments were also significantly lower. Significant differences in the c onsumption and utilization of food by fourth instars also were found a mong 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 t reatments.