Abstract: 【Aim】 To clarify the role of the newly registered fungal insecticide Cordyceps javanica JS001 in regulation of rice growth and defense against the brown planthopper, Nilaparvata lugens.【Methods】 Rice seeds were soaked with different concentrations (1×10⁴, 1×10⁶ and 1×10⁸ conidia/mL) of C. javanica JS001 conidial suspension for 48 h in laboratory, and those soaked with 0.01% Triton X-100 solution were used as the control. After 8 d of culture, the growth of rice seedlings was measured, and the behavior selection responses of N. lugens adults to rice seedlings were determined. Effects of seed soaking with 1×10⁸ conidia/mL of C. javanica JS001 conidial suspension on the contents of secondary metabolic compounds in rice seedlings were analyzed by GC-MS/MS. The rice seeds were soaked for 48 h in a C. javanica JS001 conidial suspension at the concentration of 1×10⁷ conidia/mL and clean water (control), respectively, and the individual numbers of rice planthoppers and spiders were investigated at 50 d after direct seeding in paddy fields.【Results】 The results showed that compared to the control, seed soaking in C. javanica JS001 conidial suspension at the concentrations of 1×10⁶ and 1×10⁸ conidia/mL not only significantly promoted rice seed germination, and root and shoot growth of rice seedlings, but also reduced the selectivity of N. lugens adults to rice seedlings. The results of compound analysis showed that the contents of defensive compounds such as hydrogen peroxide, oleic acid and octane were significantly higher in rice seedlings from seeds soaked with 1×10⁸ conidia/mL of C. javanica JS001 conidial suspension than those in the control. Whereas the content of 2-nononone, a compound attracting N. lugens, was significantly lower in rice seedlings from seeds soaked with C. javanica JS001 conidial suspension than that in the control. Field trials showed that, compared with the control, seed soaking with 1×10⁷ conidia/mL of C. javanica JS001 conidial suspension significantly reduced the number of rice planthoppers in paddy fields, but had no effect on the number of predatory spiders.【Conclusion】Seed soaking with C. javanica JS001 could not only promote the growth of rice seedlings, but also improve the defense of rice plants against N. lugens. Field trials further clarified the role of C. javanica JS001 in enhancing rice defense against rice planthoppers. These results can provide a new way for the application of C. javanica and the formulation of biological control strategies for rice planthoppers.

Key words: Cordyceps javanica, rice, rice planthoppers, selection behavior, biological control