“Efficacy of Metarhizium anisopliae (Metchnikoff) Sorokin against Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) under in vitro conditions”

Abstract BackgroundThe Helicoverpa armigera, Hubner (Lepidoptera: Noctuidae), is the most important economic pest. In the larval stage, the pest feeds on tomato fruits and seriously damages the fruits. Therefore, to reduce the overuse of chemical pesticides in tomato crops, microbial control is a key ingredient for sustainable crop production. Most toxic substances produced by microbial pathogens have been identified as peptides, but they are very different in terms of structure, toxicity and specificity. Therefore, the objective of the present investigation was to determine the bioefficacy of the entomopathogenic fungus, 12 Metarhizium anisopliae (Metchnikoff) Sorokin, isolates against 2nd instar larvae of the tomato fruit borer Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) under in vitro conditions. ResultsIn vitro studies an bioefficacy of 12 Metarhizium anisopliae (Metschnikoff) (Sorokin) isolates (M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11 and M12) at four different concentrations of 1x1010, 1x109, 1x108, 1x107 against 2nd instar Helicoverpa armigera (Hubner) larvae revealed that all the strains were pathogenic to the target pest at all spore concentrations. However, among them isolates M3 and M7, were most effective and recorded 95 and 85% larval mortality with LT50 value of 47.82 and 56.75 hours at the lowest spore concentration (1x1010 spores ml-1) and LC50 values of 5.06x105 and 2.29x107 spore ml−1, respectively. The lowest mortality (62.50%) was recorded in isolate M4 at 5 days after inoculation. ConclusionThese findings suggested that the adverse effect of most virulent M. anisopliae isolates M3 and M7 were compatible and most virulent to the target pest and that the simultaneous use may be helpful for managing H. armigera, 2nd instar larvae.