NOVEL PHENOXY JUVENILE-HORMONE ANALOG (PYRIPROXYFEN) SUPPRESSES EMBRYOGENESIS AND ADULT EMERGENCE OF SWEET-POTATO WHITEFLY (HOMOPTERA, ALEYRODIDAE)

The juvenoid compound pyriproxyfen is a potent suppressor of embryogenesis and adult formation of the sweetpotato whitefly, Bemisia tabaci (Gennadius). Dipping of cotton seedlings infested with 0-1-d-old eggs in 0.1 mg (AI)/liter resulted in total suppression of egg hatch. Older eggs were affected to a lesser extent. Exposure of B. tabaci females for 48 h to cotton leaves treated with 5 mg (AI)/liter pyriproxyfen resulted in oviposition of infertile eggs. This effect persisted for an additional 2 d after transfer of the females to untreated leaves and continued, although to a lesser extent, for up to 8 d. Treatment of second instars with 0.04-5 mg (AI)/liter pyriproxyfen resulted in normal development until the pupal stage; however, adult emergence was totally suppressed. At similar concentrations, the suppression of emergence from treated third instars was 91-100%. Second instars exposed to 5 mg (AI)/liter pyriproxyfen excreted honeydew at a level similar to the control until the fourth instar (pupation), after which a strong reduction was observed. Inhibition of egg hatch on the lower surface of cotton leaves was observed when their upper surface was treated with 1-25 mg (AI)/liter, indicating a pronounced translaminar effect. These findings indicate that pyriproxyfen is an efficient control agent for B. tabaci; the chemical has a strong translaminar effect and acts on all stages of this pest.