Control effects of biocontrol strain Isaria javanica on Spodoptera litura(Fabricius) and evaluation safety

【Objective】To evaluate the effects of prevention and control on Spodoptera litura(Fabricius) and the safety of Isaria javanica biocontrol strain and to provide scientific basis for its extensive application.【Method】The indoor toxicity of I. javanica to S. litura was tested with leaf immersion method. Field control effects of 2.0×10¹⁰ conidia/mL I. javanica WP to S. litura were carried out using the spray method. To evaluate the safety of 2.0×10¹⁰ conidia/mL I. javanica WP on Telenomus remus and Brassica oleracea var. capitata L. were carried out using the drug film method and the spray method, respectively.【Result】The results showed that I. javanica had a strong toxicity to the 3^rd instar larvae of S. litura. The mortality rate of larvae fed on B. oleracea leaves treated with 1.00×10⁷ conidia/mL I. javanica for 48 h reached 86.96%. The results of control effects showed that after spraying 2.0×10¹⁰ conidia/mL I. javanica WP at 900, 1125 and 1350 g/ha concentrations for 10 d, the control effects on S. litura were 73.08%, 82.77% and 83.69%, respectively. The results of safety evaluation showed that the medial lethal concentration(LC₅₀) of 2.0×10¹⁰ conidia/mL I. javanica WP for T. remus was 2.11×10⁸conidia/mL(48 h). The safety coefficient to T. remus was 5.27(t> 5), which was a low risk biological pesticide. The inhibition rate of 2.0×10¹⁰ conidia/mL I. javanica WP on the growth rate of the three cabbage varieties was less than 10.00%, and there were no visible symptoms of discoloration, necrosis, wilting, deformity, etc.【Conclusion】I. javanica has strong toxic effect on 3^rd instar larvea of S. litura, can be used as an effective and safe biological pesticide for the control of S. litura. It is suggested that 1125-1350 g/ha 2.0×10¹⁰ conidia/mL I. javanica WP can be used at occurrence period of S. litura larvea on cabbage to control the damage.