Toxicity of 14 insecticides was compared with field collected strains of the beet armyworm, Spodoptera exigua (H�bner), from locations in California, Georgia, Florida, and Texas in 1989-1991. In addition, we compared LD(50)'s of four laboratory reared strains which were considered to be susceptible to insecticides; two had been reared for 23-25 years continually in the laboratory. Beet armyworms collected from one Texas location, and Georgia and all three Florida locations were more resistant to fenvalerate and permethrin than those from California.

Beet armyworms, collected from Georgia indicated the following ascending order of toxicity: Merck MK-243 < methomyl < esfenvalerate < permethrin < methyl parathion. LD(50) values obtained with fenvalerate were significantly greater than any other insecticide tested at most locations. A high degree of variation in toxicity of permethrin to beet armyworm collected in different fields at Walnut Hill and Bascom, Florida was noted.