球孢白僵菌与低剂量化学杀虫剂对小菜蛾的协同增效作用

本文联合应用球孢白僵菌Beauveria bassiana HFW-05与低剂量化学杀虫剂，评价其是否对小菜蛾防治具有协同增效作用，为小菜蛾的有效防控提供新的途径。结果表明，低剂量的化学杀虫剂对菌株HFW-05分生孢子的萌发率、菌丝生长和胞外蛋白酶活性没有影响，甲氨基阿维菌素苯甲酸盐和氯虫苯甲酰胺的增效作用最明显。低剂量甲氨基阿维菌素苯甲酸盐和氯虫苯甲酰胺与HFW-05混用均可明显提高对小菜蛾2龄幼虫的杀虫速度。氯虫苯甲酰胺最低设定浓度10×与HFW-05 3个浓度（1.0×10⁶、1.0×10⁷、4.0×10⁷孢子/mL）混用对小菜蛾的理论LT₅₀均低于1 d，显著低于单独使用HFW-05孢悬液。甲氨基阿维菌素苯甲酸盐4×与HFW-05 3个浓度（1.0×10⁶、1.0×10⁷、4.0×10⁷孢子/mL）混用对小菜蛾的LT₅₀分别为2.4、2.2和1.2 d，显著低于单独使用HFW-05孢悬液。甲氨基阿维菌素苯甲酸盐和氯虫苯甲酰胺均没有影响HFW-05对小菜蛾的僵虫率。表明白僵菌HFW-05与低剂量甲氨基阿维菌素苯甲酸盐和氯虫苯甲酰胺联合应用，在保证白僵菌侵染作用的同时，可有效提高对小菜蛾的致病力，是防治小菜蛾的一项新的有效措施。

Synergetic Effects of Beauveria bassiana with Low Dosage Chemical Insecticides against Plutella xylostella

This study is to evaluate the synergistic effect of joint application of entomopathogenic fungi Beauveria bassiana and chemical insecticides against Plutella xylostella in laboratory, and to provide a new approach for effective control of P. xylostella. Six insecticides were evaluated for their effects on the spore germination rate, mycelial growth, sporulation rate and extracellular protease production of the strain HFW-05 in the laboratory. The results showed that low doses of chemical pesticides had no negative effects on germination rate, mycelial growth and extracellular protease activity of the conidia of the strain HFW-05, and obvious synergistic effects were observed in emamectin benzoate and chlorantraniliprole used with HFW-05. Both emamectin benzoate and chlorantraniliprole used in low-dose with HFW-05 acted more quickly against 2nd instar larvae of P. xylostella than when they were used alone. The LT₅₀ of mixture suspensions of emamectin benzoate (4×dilution) with different concentrations of HFW-05 (1.0×10⁶, 1.0×10⁷, 4.0×10⁷ spores/mL) against P. xylostella were 2.4 d, 2.2 d and 1.2 d, respectively, which was significantly shorter than those of the HFW-05 suspensions. The LT₅₀ of mixture suspension of chlorantraniliprole (10×dilution) with different concentrations of HFW-05 (1.0×10⁶, 1.0×10⁷, 4.0×10⁷ spores/mL) were all less than 1 d. Emamectin benzoate or chlorantraniliprole did not affect the muscardine cadaver rate of P. xylostella larvae infected by HFW-05. Combination of HFW-05 with low-dose emamectin benzoate or chlorantraniliprole can increase virulence of B. bassiana against P. xylostella. Therefore, it is an effective approach to control P. xylostella by combining B. bassiana HFW-05 with emamectin benzoate or chlorantraniliprole at low spray rate.