苏云金杆菌亚致死浓度对美国白蛾及其寄生蜂生长发育的影响

为阐明苏云金杆菌Bacillus thuringiensis(Bt)与白蛾周氏啮小蜂Chouioia cunea Yang的协同作用,分别用103~108孢子/m L的6个Bt浓度处理美国白蛾Hyphantria cunea 2龄幼虫后,通过室内试验测定了Bt对其致死、亚致死效应,及亚致死浓度Bt对寄生蜂子代出蜂的影响。结果表明,浓度106孢子/m L处理组美国白蛾均未能化蛹;而106孢子/m L处理组均能化蛹并羽化,且幼虫发育历期随Bt浓度的增加而延长,平均蛹重在74.92~92.18 mg之间,均高于对照的68.66 mg,但蛹重不呈线性规律变化。当Bt对美国白蛾平均校正死亡率低于17.17%时,幼虫发育历期延迟不明显,但平均蛹重为101.11~124.34 mg,均高于对照;接蜂后能够正常出蜂,出蜂率为33.13%~51.25%,每蛹出蜂量为117.43~143.42头,均显著高于对照。表明用平均校正死亡率低于20%的Bt处理对白蛾周氏啮小蜂的寄生有利,2种生防措施协同作用存在增效潜力。

Effects of sublethal concentration of Bt on development of Hyphantria cunea and the parasitic wasp Chouioia cunea Yang

To evaluate the synergetic effect of Bacillus thuringiensis (Bt) and Chouioia cunea Yang on controlling the fall webworm, Hyphantria cunea, the experiments were conducted to explore the effects of Bt levels on H. cunea's development and the ecolsion of C. cunea when the 2nd instar larvae was exposed to solution with different concentrations of Bt (10³-10⁸ cells/mL). The results showed that the pupae and adults of H. cunea were obtained with the larval duration delayed when Bt concentrations were lower than 10⁶ cells/mL. On the contrary, no pupae and adults were formed when the Bt concentration was higher than 10⁶ cells/mL. The average pupal weights of H. cunea were 74.92-92.18 mg, not linearly distributed, but heavier than that of control at 68.66 mg with diets containing less than 10⁶ cells/mL. Moreover, the average pupal weights of H. cunea were 101.11-124.34 mg, higher than that of the control at 79.56 mg with the corrected mortality less than 17.17% of Bt. The parasitic rate and the amount of C. cunea demonstrated the same tendency as the former. The emergence rates and the amount of wasp were significantly higher than the control with 33.13%-51.25% and 117.43-143.42 per pupa, respectively. These experiments indicated that the method combining Bt treatment (ess than 20% corrected mortality) with C. cunea application was synergetic against H. cunea in practice.