Whiteflies’ remarkable ability to transmit and spread viruses has had a great impact on global food production and thus they have become one of the most serious crop pests throughout much of the world. The ability of the whitefly to survive in extreme subtropical climates is related to the regulation of the enzyme, superoxide dismutase (SOD). The purpose of our study is to establish a correlation between stress and SOD activity. SOD functions in the conversion of O₂^- free radicals to less toxic products. Superoxide free radicals bind to macromolecules in cells and may lead to breakdown of cellular membranes. In previous experiments, using an electrophoretic assay, we have shown under normal metabolic conditions the presence of superoxide dismutase in Bemisia tabaci whole body extracts. In this study, we determined the effects of heat stress on whiteflies by characterization and quantification of SOD activity using a commercially available spectrophotometric SOD assay in conjunction with the electrophoretic assay and computer aided densitometry. In the spectrophotometic assay, activity of SOD was determined by inhibition of the enzyme in an O₂^- dependent reaction. Our data showed that SOD activity was directly proportional to an increase in temperature. The same was observed for SOD isozymes in the electrophoretic assay. Our results imply that SOD plays a vital role in whitefly survival in areas with extremely high temperatures. Currently we are using whiteflies fed on begmovirus-infected plants to test our hypothesis that SOD activity increases in viruliferous whiteflies.