Spinosad was evaluated against laboratory colonies of tobacco budworm, Heliothis virescens (F.), and beet armyworm, Spodoptera exigua (Hübner), using the adult vial test (AVT). Tobacco budworm adults were more susceptible (>12-fold) to spinosad than beet armyworm adults. Bollworm, Helicoverpa zea (Boddie), and tobacco budworm field populations also were monitored for susceptibility to spinosad in Louisiana during 2000. An increase in survival of male tobacco budworm moths exposed to the 5 µg/vial concentration was observed compared to data from 1991 to 1993. Survival at the 15 µg/vial concentration during 2000 was similar to that observed during 1991 to 1993. Studies also were conducted to determine the response of laboratory colonies of pest insects to indoxacarb and S-1812 using the AVT and diet overlay procedures. Dose-mortality values of indoxacarb and S-1812 for bollworm, tobacco budworm, beet armyworm, and fall armyworm, Spodoptera frugiperda (J.E. Smith), were higher than the respective values for cypermethrin in the AVT. In response to these findings, indoxacarb and S-1812 were evaluated in a diet insecticide overlay bioassay against 2-day old first instar larvae of each species. S-1812 demonstrated greater activity against tobacco budworm (4.9-fold) and beet armyworm (6.2-fold) larvae compared to indoxacarb. Bollworm larvae
(4.2-fold) were more sensitive to indoxacarb than S-1812. Both compounds were equally toxic against fall armyworm larvae. These studies indicate that the AVT is not appropriate for use with indoxacarb or S-1812. These studies also provide valuable information for use in developing insect resistance monitoring programs.