Fourth International Bemisia Workshop International Whitefly Genomics Workshop
Spiromesifen: A New Pest Management Tool for Whitefly Management
Department of Entomology, University of California, Riverside, CA, USA. Correspondence: nilima.castle@ucr.edu
During the last two decades, there have been a number of changes in whitefly management worldwide. Previously broad-spectrum insecticide applications were recommended, based on the population dynamics of whiteflies, leading to resistance problems in some cases. At present, a number of options in chemical control are available for managing whiteflies through development of integrated pest management programs that include use of safer, more selective insecticides with narrow spectrum of activity that may be compatible with beneficial insects. Some of the newer insecticides, including insect growth regulators, neonicotinoids, sodium channel blockers and tetronic acids, are more selective and reported to be compatible with use of many kinds of natural enemies. The enhancement of natural enemy populations in a cropping system can add additional mortality factors and promote integration of chemical and biological control components of IPM programs. Spiromesifen is a member of a recently introduced class of selective chemistry, tetronic acids, with broad spectrum insecticidal and acaricidal activity against whiteflies and spider mites. Its mode of action is by inhibition of lipid biosynthesis that affects the egg and immature stages of these pests. Foliar sprays of spiromesifen are reported to be effective against whiteflies in cotton, vegetables and ornamentals. The present study was conducted to evaluate the efficacy of spiromesifen against a number of natural populations of Bemisia argentifolii from California and Arizona and against imidacloprid-resistant whiteflies, to establish baseline toxicity data. Baseline toxicity data for spiromesifen against B. argentifolii populations have been collected for consideration as part of future whitefly resistance management program. The test populations were all ‘B’ biotypes with the exception of a ‘Q’ biotype from Spain held in quarantine at UC Riverside. The compound was effective against all immature stages of whiteflies but exhibited geographical susceptibility differences. However, spiromesifen was significantly more active against early instars of whiteflies based on lowest LC50s recorded. Spiromesifen was highly effective against the ‘Q’ type strain from Spain, which is highly resistant to neonicotinoids, suggesting the absence of cross-resistance between the two classes of chemistry. Spiromesifen also showed reduced oviposition and egg hatch in an imidacloprid-resistant strain. Spiromesifen appears to be safe to Eretmocerus eremicus under greenhouse conditions. Results of this study suggest that spiromesifen has no cross-resistance to more commonly used neonicotinoids and appears to provide a more compatible environment for biological control of whiteflies. Therefore, spiromesifen can be added to the arsenal of chemistries that are currently available for whitefly management. Spiromesifen can be considered to be an ideal candidate for whitefly resistance management programs in rotation with chemistries with other modes of action and minimize current problems in controlling whiteflies in various parts of the world.