印楝素不同处理方法对烟粉虱的室内毒力测定

 【目的】明确印楝素及其不同施药方式对烟粉虱各虫态的致死作用。【方法】采用黄瓜叶片浸液法和叶柄内吸法测定了0.3%印楝素乳油对烟粉虱成虫、1日龄卵、5日龄卵和1～4龄若虫的室内毒力。【结果】在所测试的浓度范围（0.3125～10.0 mg?L-1）内，两种处理方式下烟粉虱各虫态的校正死亡率均随印楝素浓度的增大而顺次显著增大，印楝素叶片浸液处理的校正死亡率高于叶柄内吸处理。印楝素叶片浸液处理对烟粉虱成虫、1日龄卵、5日龄卵、1龄若虫、2龄若虫、3龄若虫、4龄若虫的致死中浓度LC50值分别为3.0246、2.2019、5.7109、0.5909、0.7465、1.6948和2.6603 mg?L-1，而叶柄内吸处理的LC50值分别为6.016、4.0321、6.0537、0.8614、0.9941、2.2419和4.4533 mg?L-1。【结论】印楝素叶片浸液处理对烟粉虱各龄若虫的致死作用均高于叶柄内吸处理，烟粉虱低龄若虫期是采用印楝素防治的最佳时期。印楝素乳油可望成为防治烟粉虱的重要药剂之一。

Toxicity of Foliar or Systemically Applied Azadirachtin to Bemisia tabaci Gennadius (Homoptera, Aleyrodidae)

【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.