Sublethal Effects of Spiromesifen on Reproduction and Egg Development in Bemisia tabaci Mediterranean Cryptic Species

Spiromesifen is a nonsystemic insecticide that has been primarily recognized for its efficacy against immature stages of whiteflies and mites. However, its activity against adult and egg stages has been less well characterized. In this study, we evaluated its sublethal effects on the reproduction and egg development of the Mediterranean (MED) cryptic species of Bemisia tabaci (Hemiptera: Aleyrodidae). Leaf-dipping bioassays demonstrated that spiromesifen causes significantly higher mortality in nymphs than in eggs and adults. Beyond direct lethality, adult exposure to spiromesifen-treated tomato leaves reduced oviposition rates and disrupted egg development, inducing abnormal egg morphologies in 39.2% and 58.5% of the eggs, respectively, compared with the untreated control. In addition, as the exposure duration increased, egg hatchability declined proportionally, reaching 50.2% compared with the untreated control. These results indicate that spiromesifen has both lethal and sublethal impacts on B. tabaci, combining direct mortality with reproductive suppression. Such dual effects highlight spiromesifen as a promising tool for integrated pest management (IPM) programs, provided it is used judiciously within resistance management frameworks.