Abstract: 【Objective】We tested mortality and LC50 of 0.3% azadirachtin (AZ) EC against sweetpotato whitefly, Bemisia tabaci, 【Method】by both cucumber leaf disc dipping method and petiole wrapping method. 【Result】Mortalities of whiteflies treated by AZ disc dipping method were higher than that treated by petiole wrapping method at the tested AZ concentrations between 0.3125 mg/L and 10.0 mg/L, and that mortalities of whiteflies in both the tow bioassay methods were significantly dosage-dependent. The medium lethal concentration (LC50) of AZ by disc dipping method to adults, 1 day old eggs, 5 days old eggs, 1st instar nymphs, 2nd instar nymphs, 3rd instar nymphs and 4th instar nymphs were 3.0246, 2.2019, 5.7109, 0.5909, 0.7465, 1.6948 and 2.6603 mg / L, respectively, and the LC50 of AZ treated by petiole wrapping method were 6.016, 4.0321, 6.0537, 0.8614, 0.9941, 2.2419 and 4.4533 mg / L, respectively. Therefore, foliar application of AZ is expected to achieve higher control of sweetpotato whitefly than systemic application; young nymph is the window stage for whitefly control by AZ. 【Conclusion】AZ provides an alternative to chemicals in control sweetpotato whitefly.

Key words: Azadirachtin, Bemisia tabaci, Dipping bioassay, Systemic bioassay, Toxicity