Pathogenicity of some commercial formulations of entomopathogenic fungi on the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a major threat to tomato production in Rwanda. Laboratory bioassays were conducted to evaluate some commercial entomopathogenic fungi (EPF) formulations on T. absoluta larvae. The larvae, inside the leaf galleries, were obtained from the established tomato field. Commercial EPF: Metatech (R) WP [Metarhizium anisopliae (Metschn.) Sorok, Strain FCM Ar 23B3], Beauvitech (R) WP [Beauveria bassiana (Bals.) Vuill., Strain J25], and Botanigard ES [B. bassiana (Bals.), Strain GHA] were tested in Petri dishes against T. absoluta larvae at a concentration of 10(8) spores/ml. A synthetic insecticide, imidacloprid was included for comparison as a positive control, while water was used as a negative control. All the tested commercial EPF formulations were pathogenic to T. absoluta larvae in all conducted bioassays. Mortality rates increased with an increase in time (days). However, the insignificant difference was observed in the mortality of T. absoluta larvae treated with the commercial EPF during the first 3 days in all bioassays. Highly significant differences (p < 0.01) in pathogenicity among treatments were observed from the 4th to 6th days after inoculation. Metatech (R) WP and Beauvitech (R) WP recorded the highest mortality rates (82.8 and 60.8%) with the LT50 values of 3.9 and 5.2 days, respectively, while imidacloprid caused the least larval mortality. Since the EPF demonstrated high virulence level against the target pest, the efficacy of Metatech (R) WP and Beauvitech (R) WP should be advanced to field evaluation to determine their potential as alternatives to the synthetic insecticides.