PYRIPROXYFEN, A POTENT SUPPRESSOR OF EGG HATCH AND ADULT FORMATION OF THE GREENHOUSE-WHITEFLY (HOMOPTERA, ALEYRODIDAE)

Pyriproxyfen is a potent suppressor of egg viability and adult formation of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Exposure of T. vaporariorum adults to tomato seedlings treated with various concentrations of pyriproxyfen resulted in LC(50) of 0.12 and 0.10 mg (AI)/liter for suppression of egg hatch and adult emergence, respectively. Dipping of tomato seedlings infested with 0-1-d-old eggs or with first-instar larvae in various concentrations of pyriproxyfen resulted in LC(50) values of 0.043 and 0.036 mg (AI)/liter, respectively. Eggs >3 d old were not affected. Pyriproxyfen has no direct effect on the larval stages but suppresses adult emergence. First and third instars treated with 0.0025-0.04 mg (AI)/liter pyriproxyfen pupated normally; however, a suppression of 57 and 100% in adult emergence was observed when first and third instars were treated, respectively, with 0.04 mg(AI)/liter. With all tested concentrations, third instars were more susceptible than first instars. Reduction in egg hatch on the lower surface of tomato leaves when the upper surfaces were treated with 5 and 25 mg (AI)/liter, indicates a translaminar effect. Our findings indicate that pyriproxyfen affects all stages of T. vaporariorum either directly (ovicidal) or indirectly (transovarial and suppression of adult formation upon treatment of larvae) and could be considered a potential compound for controlling T. vaporariorum in vegetables and ornamentals.