The effect of temperature on activity of insecticides for controlling grasshoppers in leafy green vegetables was evaluated. Insecticides evaluated had differing modes of action and included diflubenzuron, azadirachtin, Beauveria bassiana, spinosad, endosulfan, esfenvalerate, and naled. We evaluated these insecticides for efficacy to third instar differential grasshopper at temperatures ranging from 10 to 35 degrees C. In the laboratory, esfenvalerate resulted in 100% mortality at each temperature and efficacy was not temperature dependent. Treatment with spinosad resulted in similar mortality as with esfenvalerate at all temperatures except 10 degrees. The activity of B. bassiana was greatest at 25 degrees, and was adversely affected by high and low temperatures. Treatment with diflubenzuron resulted in increased mortality at high temperatures. The activity of azadirachtin ranged from 19 to 31% and was not influenced by temperature. In field studies, spinosad, diflubenzuron, and esfenvalerate provided significant levels of mortality both at-application and when nymphs were exposed to 1-h old residues. However, only spinosad and diflubenzuron provided similar levels of mortality when nymphs were exposed to 24-h old residues. The residual activity of endosulfan, naled, esfenvalerate, and spinosad decreased with increasing time (0 to 24 hours) after exposure to sunlight and high summer temperatures. Naled had a short residual activity period and activity was dependent upon immediate contact with the nymphs. Beauveria bassiana was inactive under high temperatures and intense sunlight.