Temperature-Dependent Growth and Virulence, and Mass Production Potential of Two Candidate Isolates of Metarhizium anisopliae (Metschnikoff) Sorokin for Managing Maruca vitrata Fabricius (Lepidoptera: Crambidae) on Cowpea

Entomopathogenic fungi are increasingly gaining recognition as a viable alternative to synthetic insecticides for pest management; their efficacy is influenced by several biotic and abiotic factors. In this study, the effect of temperature on germination, growth and virulence of two isolates of Metarhizium anisopliae, ICIPE 18 and ICIPE 69, against first-instar larvae of Maruca vitrata at temperatures ranging from 15–35 °C, and mass-production potential of the isolates were assessed under laboratory conditions. Minimum, optimum and maximum threshold temperatures for efficacy of the best performing isolate, ICIPE 69, were estimated by the quadratic equation which emerged as the best model among the nonlinear mathematical expressions tested. Neither isolate germinated at 15 °C while germination was low at 35 °C for both. The optimum temperature for germination, radial growth and virulence of ICIPE 69 and ICIPE 18 ranged between 25–30 °C and 25–33 °C, respectively. Mortality of M. vitrata by both isolates ra...