保幼激素类似物苯氧威对异色瓢虫不同发育阶段的影响

【目的】本研究旨在明确保幼激素类似物苯氧威对天敌异色瓢虫Harmonia axyridis的影响, 并探讨其作用机理, 以便进行安全性评价并为科学使用提供理论依据。【方法】应用连叶浸渍法、浸渍法、点滴法和药膜法分别处理异色瓢虫卵、2龄幼虫、蛹和成虫, 观察苯氧威对4个虫态的影响。【结果】用浓度为0.0001 μg/mL的药液处理初产卵, 能抑制胚胎的发育; 但用高达20 000 μg/mL的药液处理发育2 d的卵, 幼虫仍可正常孵化; 用浓度高达4 000 μg/mL的药液浸渍2龄幼虫, 对幼虫的致死作用极小; 用浓度为0.0001 μg/头的药液处理当天蛹, 形成蛹 成虫中间体, 羽化的成虫畸形; 用浓度为0.0125 μg/mL的药液处理成虫, 24 h后成虫的生命力受到明显影响。【结论】苯氧威对异色瓢虫初产卵有明显的毒杀作用, 严重阻碍蛹到成虫的变态和影响成虫的存活。在田间使用该杀虫剂时, 要避开异色瓢虫的敏感期。

Effects of fenoxycarb,a juvenile hormone analog,on various developmental stages of Harmonia axyridis (Pallas) (Coleoptera:Coccinellidae)

[Objective] This study focused on the effects of fenoxycarb, a juvenile hormone analog (JHA), on the ladybird Harmonia axyridis and discussed its mechanisms of action, so as to evaluate the risks of fenoxycarb application and provide theoretical basis for rational use of the JHA. [Methods] Toxicity of fenoxycarb to egg, 2nd instar larva, pupa and adult of H. Axyridis was determined in the laboratory by using the methods of dipping, topical contact and residual film, respectively. [Results] Fenoxycarb significantly disrupted embryonic development of newly-laid eggs at the minimum concentration of 0. 0001 μg/mL, but when the 2 d-old eggs were treated, the larvae could hatch even at the highest concentration of 20 000 μg/mL. The mortality of 2nd instar larvae was very low even at the highest concentration of 4 000 μg/mL. When pupae were treated, fenoxycarb had significant effects on pupal development with adult eclosion blocked, and pupa-adult intermediate and abnormalities of adults emerged at the minimum concentration of 0.0001 μg (a. I.)/larva. The adult vitality was affected significantly at 24 h after contact with fenoxycarb at the concentration of 0. 0125 μg/mL. [Conclusions] Fenoxycarb had an obvious ovicidal action on newly-laid eggs of H. Axyridis, seriously blocked the larval-pupal metamorphosis and affected the survival of the adults. When fenoxycarb is used in fields, the susceptible developmental stages of the ladybird should be avoided.