莱氏绿僵菌FJMR2对草地贪夜蛾不同虫态的致病性研究

The pathogenicity of Metarhizium rileyi FJMR2 to different age classes of Spodoptera frugiperda

【目的】为明确莱氏绿僵菌Metarhizium rileyi FJMR2对草地贪夜蛾Spodoptera frugiperda的生物防治潜力。【方法】在室内条件下,采用浸渍法测定了莱氏绿僵菌FJMR2对草地贪夜蛾卵、幼虫和蛹的致病性。【结果】当孢子浓度为2×10^(8)孢子/mL时,草地贪夜蛾1-5龄幼虫和蛹的校正死亡率分别为100%、95.78%、87.15%、64.67%、38.00%和93.93%;草地贪夜蛾1-5龄幼虫和蛹的LC_(50)分别为3.12×10^(4)、7.94×10^(4)、2.24×10^(6)、2.13×10^(7)、7.46×10^(8)和1.25×10^(5)孢子/mL。LT_(50)随孢子浓度的增大而缩短、随幼虫虫龄的增长而延长,当孢子浓度为2×10^(8)孢子/mL时,草地贪夜蛾1-5龄幼虫和蛹的LT_(50)分别为3.93、4.32、5.62、7.18、9.40和4.45 d。卵期为0 h和24 h的草地贪夜蛾卵经莱氏绿僵菌FJMR2浸渍处理后,孵化率分别为84.53%和89.77%,初孵化3 d的幼虫存活率分别为1.81%和3.02%,均显著低于对照组。【结论】莱氏绿僵菌FJMR2对草地贪夜蛾1-4龄幼虫和蛹具有较强侵染致病能力,同时显著降低卵的孵化率和初孵幼虫存活率。

[Objectives]To evaluate the potential of Metarhizium rileyi FJMR2 as a biocontrol agent for Spodoptera frugiperda.[Methods]The pathogenicity of FJMR2 to the larvae,pupae and eggs of S.frugiperda was tested using the leaf dipping method under laboratory conditions.[Results]A spore concentration of 2×10^(8) spores/mL achieved a corrected mortality of 1st to 5th instar larvae and pupae of 100%,95.78%,87.15%,64.67%,38.00% and 93.93%,respectively.LC_(50) values of 1st to 5th instar larvae and pupae were 3.12×10^(4),7.94×10^(4),2.13×107,7.46×10^(8) and 1.25×10^(5) spores/mL,respectively.LT_(50) values decreased with increasing spore concentration and increased with larval instar.At a spore concentration of 2×10^(8) spores/mL,LT_(50) values of 1st to 5th instar larvae and pupae were 3.93,4.32,5.62,7.19,9.41 and 4.45 d,respectively.In addition,the hatching rate of 0-hour-old eggs and 24-hour-old eggs were 84.53% and 89.77%,respectively,and the survival rates of newly hatched larvae inoculated with FJMR2 were 1.81% and 3.02%,respectively;significantly lower than that of the control.[Conclusion]The FJMR2 strain was highly pathogenic to 1st to 4th instar larvae and pupae of S.frugiperda,reducing both the hatching rate of eggs and the survival rate of newly hatched larvae.It consequently has high potential as a biological control for S.frugiperda.