卵孢白僵菌及添加杀虫助剂对两种地老虎的生物活性测定

【目的】确定卵孢白僵菌Beauveria brongniartii菌株NEAU30503对八字地老虎Xestia c-nigrum(Linnaeus)和小地老虎Agrotis ypsilon(Rottemberg)的杀虫活性。【方法】采用浸叶法测定NEAU30503对地老虎低龄幼虫的生物活性,土壤处理法测定对高龄幼虫的杀虫活性。【结果】NEAU30503对5日龄八字地老虎幼虫第15天毒力回归方程为y=0.6568x-0.1636(r=0.9846),其LC_(50)、LC_(80)分别为7.28×10~7孢子/m L、139.14×10~7孢子/m L;对5龄八字地老虎幼虫毒力回归方程为y=1.0929x-3.2893(r=0.9801),其LC_(50)、LC_(80)分别为3.85×10~7孢子/L、22.65×10~7孢子/L。未死幼虫化蛹后仍有部分蛹死于白僵菌感染,并能明显降低成虫羽化率。白僵菌与Bt、茶皂素、以及亚致死剂量的高效氯氢菊酯和阿维菌素混用能明显提高其杀虫活性和杀虫速度。【结论】NEAU30503对地老虎具有较高的杀虫活性,土壤处理防治高龄幼虫效果好,喷雾处理防治低龄幼虫加入少量的高效氯氢菊酯或茶皂素效果明显。本研究为开展白僵菌田间防治地老虎提供了科学依据。

Toxicity of Beauveria brongniartii to two cutworm species

Objectives] To determine the toxicity of the Beauveria brongniartii strain NEAU30503 to larvae of the spotted and black cutworm. Methods] The leaf dipping method was used to determine the toxicity of NEAU30503 to young cutworm larvae and the soil treatment method to determine its toxicity to older instar larvae. Results] The toxicity of NEAU30503 to 5-day-old larvae of spotted cutworm at day 15 post infection can be expressed by the regression equation y=0.6568x-0.1636 (r=0.9846). The LC50 and LC80 were 7.28×107 conidia/mL and 139.14×107 conidia/mL, respectively. The toxicity of NEAU30503 to 5th instar spotted cutworm larvae can be expressed by the regression equation y=1.0929x-3.2893 (r=0.9801), with LC50 and LC80 of 3.85×107 conidia/L and 22.65×107 conidia/L, respectively. NEAU30503 was lethal to cutworm pupae, and clearly decreased the eclosion rate of cutworms. When NEAU30503 was mixed with tea saponin, the sublethal dose of beta-cypermethrin and abamectin could significantly increase the toxicity to black cutworms. Conclusion] The NEAU30503 strain was the most toxic to cutworms. NEAU30503 was more toxic to older instar larvae when delivered via the soil. When sprayed, a mixture of NEAU305035 with a sublethal dose of beta-cypermethrin or tea saponin had a significant effect on young cutworm larvae. This study provides a scientific basis for using Beauveria sp. to controll cutworms in the field.