SUSCEPTIBILITY OF THE SWEET-POTATO WHITEFLY (HOMOPTERA, ALEYRODIDAE) TO BUPROFEZIN DURING THE COTTON SEASON

The susceptibility of the sweetpotato whitefly, Bemisia tabaci (Gennadius), to buprofezin (an insect growth regulator) was examined during the 1990 cotton growing season at various locations in Israel. Bioassays were done with field-collected adults exposed for 48 h to treated cotton seedlings. We determined oviposition and cumulative egg and larval mortality until pupation. After 2 yr of field application of buprofezin, no resistance could be detected. A slight increase in tolerance to buprofezin had occurred after two applications during the growing season, resulting in a 1.4- to 2.1-fold increase in LC50s, and a 2.6- to 2.9-fold increase in LC90s. Comparisons between two assays done at the end of the cotton seasons of 1989 and 1990, respectively, showed no significant difference in sweetpotato whitefly susceptibility. Lack of significant differences apparently resulted from restriction of buprofezin use to 1 mo during the cotton growing season. This restricted use was in accordance with the insecticide resistance management (IRM) strategy. A 6-fold resistance of sweetpotato whitefly to endosulfan, observed in a cotton field, did not alter the tolerance to buprofezin. Our data describe baseline susceptibility of this insect to buprofezin.