We studied the management of resistance to the insect growth regulator pyriproxyfen in the sweet-potato whitefly, one of the world's most devastating crop pests, using a simulation model. Pyriproxyfen is a key "environmentally-friendly" insecticide that improves whitefly control in several crops, reduces the dependence on potentially dangerous broad-spectrum insecticides, contributes in preserving beneficial species, and increases farmer profits. We studied the effects of concentration, amount of land planted to pyriproxyfen, and several other key biological factors on the evolution of resistance. Results from the project will be used to develop new management strategies for controlling the sweet-potato whitefly using environmentally benign tactics.