Effect of the Insect Growth Regulator Novaluron (Pedestal) on Silverleaf Whitefly Reproduction

Abstract

Insect growth regulators, which are primarily used to kill the larval stages of certain insect groups, have indirect effects on the adult stage of whiteflies. In this study, we assessed the effect of the insect growth regulator novaluron (Pedestal) on the reproduction of silverleaf whitefly (Bemisia argentifolii). Two experiments were conducted by exposing adult female silverleaf whiteflies to the low [0.47 mL·L-1 (6 floz/100 gal)] and high [0.63 mL·L-1 (8 floz/100 gal)] label-recommended rates of novaluron. There was also an untreated control. Infested plants [mist flower (Eupatorium coelenstinum) and transvaal daisy (Gerbera jamesonii) for Expt. 1 and Expt. 2, respectively] containing adult female silverleaf whiteflies were sprayed with novaluron using a carbon dioxide (CO2) backpack sprayer. Plants were immediately placed into cages covered with antivirus insect screening. After 24 hours, six adult female silverleaf whiteflies were aspirated from the treated plants, and immobilized with CO2 before being placed onto untreated plants [transvaal daisy for Expt. 1, and rose-of-china (Hibiscus rosa-sinensis) for Expt. 2]. Three munger cells containing two adult female silverleaf whiteflies per cell were attached to leaves of each of the untreated plants. The number of live and dead eggs, and live nymphs per plant was assessed 4 and 8 days after treatment (DAT). In Expt. 1, the low rate of novaluron significantly reduced egg viability compared to the untreated control based on live nymphal counts 8 DAT. In Expt. 2, both rates of novaluron significantly reduced egg viability compared to the untreated control, based on live nymphal counts and number of dead eggs 8 DAT. The results from this study indicate that novaluron negatively affected female silverleaf whitefly reproduction by reducing egg viability, which may decrease the number of silverleaf whiteflies produced during a cropping cycle. This is an important long-term pest management strategy that may reduce the number of insecticide applications and decrease labor costs.