Research Reports: Effect of Soil Parameters on Pathogenicity of the Fungus Metarhizium Anisopliae to the Sugarcane Grub Ligyrus Subtropicus (Coleoptera: Scarabaeidae)
The effect of soil temperature, soil moisture, and inoculum concentration on pathogenicity of Metarhizium anisopliae to the sugarcane grub, Ligyrus subtropicus (Blatchley) was tested under laboratory conditions. M. anisopliae killed grubs from 16 to 31@* C as defined by the equation Y = -1.04 + 0.06X where Y = percentage grub mortality and X = soil temperature (C@*). M. anisopliae also killed grubs at soil moistures from 0.17 to 1.0 gravimetric weight (weight water/weight oven dry soil) as defined by the equation Y = -0.42 + 3.59X - 2.68X@^2 where Y = percentage grub mortality and X = soil moisture. Grubs were killed by M. anisopliae at inoculum concentrations (conidia/gr. oven-dry soil) from 10 to 12,500 as defined by the equation Y = 0.108 + 0.00006X where Y = percentage grub mortality and X = inoculum concentration. The relevance of the results to field conditions in Florida sugarcane fields and the potential for M. anisopliae controlling L. subtropicus are discussed.