The Virulence of Metarhizium to Spodoptera litura in Different Areas of Western Yunnan

PurposeExcellent Metarhizium strain with high virulence to Spodoptera litura was screened to provide alternative material for green prevention and control of S. litura.

MethodThe 3rd instar larvae were inoculated by crawling infection way with 15 Metarhizium species from different areas of Western Yunnan (Baoshan, Nujiang, Dali and Chuxiong) to test their virulence. The virulence of the screened excellent strain was analyzed under different temperature (14-35 ℃).

ResultAll the 15 Metarhizium species had virulence to S. litura and the corrected mortalities of the larvae were 30%-100%. Six Metarhizium species (Metarhizium rileyi BUM1209, M. brunneum BUM 22, M. anisopliae BUM1900, M. baoshanense BUM634, M. pingshaense BUM701, M. guizhouense BUM119) had higher virulence (with 100% of corrected mortalities). Among which, M. rileyi BUM1209 from Baoshan had the fastest lethality speed and the highest virulence (LT₅₀=4.88 d, total lethal time=6.92 d). M. rileyi BUM1209 caused 100% corrected mortalities to 3rd instar larvae under different temperature. Its lethality speed was the fastest at 26 ℃ (LT₅₀=2.94 d, total lethal time=5.90 d). Its virulence would be significantly weakened if the temperature increase or decrease. The lethality speed was the slowest at 14 ℃ (LT₅₀=7.90 d, total lethal time=15.75 d).

ConclusionM. rileyi BUM1209 had the best virulent effect against S. litura and its optimum infection temperature was 26 ℃. The strain had good development and utilization potential.