Greenhouse studies were conducted to determine the most vulnerable white-fly stage to various pyrethroid treatment regimes and to determine if differ-ences in insecticide efficacy are due to speed of kill. The order of immature whitefly susceptibility overall was crawler to second instar > egg hatch to crawler > 3rd-4th instar to redeye nymph. All insecticide treatments tested appeared to take approximately the same length of time to take lethal action. Small plot field trials were conducted in 1994 to evaluate season long control of whitefly with competitive pyrethroid combinations and in 1995 to compare the efficacy of rotating nonpyrethroid and pyrethroid insecticide combinations with continuous pyrethroid insecticide treatment regimes. Large field plots also established in 1995 determined Mustang 1.5 EW whitefly efficacy improves ± 5% when a surfactant is added (CSO or Bivert) or the rate of Orthene is increased (2X) in insecticide tankmixtures applied by air.