A resistance monitoring technique using yellow sticky cards sprayed with insecticides detected resistance to bifenthrin and endosulfan in four field populations of Bemisia tabaci (Genn.) from the Imperial Valley. Resistance levels to bifenthrin were moderate, up to 14x top label rate. Methomyl, endosulfan and chlorpyrifos were found to be effective against adult whiteflies. Mixtures of bifenthrin with endosulfan or methomyl were found to be very toxic to adults. Resistance levels did not increase under experimental conditions using mixtures of compounds. A rotation scheme of bifenthrin-endosulfan-chlorpyrifos delayed the onset of resistance in adults, suggesting that rotating insecticidal treatments is advantageous in preserving efficacy of insecticides.