Sweetpotato whitefly (SPWF) Bemesia tabaci Gennadius strain B has been a devastating pest of cotton in Arizona and California in recent years. Management systems involving cultural procedures, SPWF population monitoring, crop sanitation, crop sequencing, chemical control and other technology are developing slowly. Action thresholds in relation to cotton yield and quality losses are urgently needed. Preliminary studies with cotton insecticide treatments initiated each week from shortly after cotton seedling emergence to late in the cotton season were conducted at the Irrigated Desert Research Station, Brawley, CA in 1993. The results suggest the best action threshold for our studies in relation to cotton yield was 0.22 SPWF nymph/cm² of leaf disc from sampled leaves in control and insecticide treated plots. However, preliminary action thresholds were also developed for SPWF eggs, pupae and adults. Cotton lint stickiness and cotton defoliation were also highly and negatively correlated to SPWF populations.