Can Bacillus thuringiensis affect the biological variables of natural enemies of Lepidoptera?

ABSTRACT: The entomopathogen Bacillus thuringiensis (Bt) is widely used as one of the ingredients in pest control formulations, but researches conducted on its effect on non-target organisms are still in the nascent stage. This investigation aimed to uncover if Bt treated with Tenebrio molitor (Coleoptera: Tenebrionidae) larvae and pupae could affect the biological variables of Podisus nigrispinus (Hemiptera: Pentatomidae) and Palmistichus elaeisis (Hymenoptera: Eulophidae), all of which established natural enemies of leaf defoliator caterpillars in the eucalyptus culture. Larvae of T. molitor were fed on wheat bran containing different concentrations of B. thuringiensis (0.00; 0.25; 0.50; 1.00; 2.00 and 4.00 g Agree/kg bran). When the larvae attained size of about 2 cm, they were used as prey for P. nigrispinus (Bioassay I), and their pupae used as hosts for P. elaeisis (Bioassay II). Only the biological variables oviposition period and egg numbers by posture of the predator P. nigrispinus were altered. The biological variables of P. elaeisis were not altered, since it was possible to use these control methods within the integrated pest management.

摘要：昆虫病原苏云金杆菌（Bacillus thuringiensis，Bt）作为害虫防治制剂的常用组分应用广泛，但针对其对非靶标生物的影响研究仍处于起步阶段。本研究旨在探究经黄粉虫（Tenebrio molitor，鞘翅目Coleoptera：拟步甲科Tenebrionidae）幼虫与蛹处理的Bt，是否会影响桉树栽培体系中叶食性毛虫的两类自然天敌——暗黑蝽（Podisus nigrispinus，半翅目Hemiptera：蝽科Pentatomidae）与榄仁树旋小蜂（Palmistichus elaeisis，膜翅目Hymenoptera：旋小蜂科Eulophidae）的生物学指标。
本研究以添加不同浓度Bt制剂（0.00、0.25、0.50、1.00、2.00与4.00 g Agree/kg麦麸）的麦麸饲喂黄粉虫幼虫；待幼虫体长至约2 cm时，将其作为猎物用于暗黑蝽的生物测定试验I，同时将黄粉虫蛹作为寄主用于榄仁树旋小蜂的生物测定试验II。
结果显示，仅捕食性天敌暗黑蝽的产卵历期与单雌产卵量发生显著变化，而榄仁树旋小蜂的各项生物学指标未受影响。综上，该Bt处理方式可安全应用于害虫综合治理体系。