Efficacy of Metarhizium Anisoplae (Metschnikoff, Sorokin) on the senegalese grasshopper oedaleus senegalensis (Krauss, 1877) in its Natural Environment

The Senegalese grasshopper Oedaleus senegalensis (Krauss, 1877) is a serious agricultural pest in Senegal. The use of chemical pesticides on a large scale has raised concerns because of side effects on health and the environment. As an alternative to chemical control, a fungal strain of Metarhizium anisopliae (Metschnikoff, Sorokin) was isolated from the Senegalese grasshopper, and grown in agar culture medium. The effect on O. senegalensis was studied with an oil fungus formulation of 340 × 105 conidia/ml. Spraying took place in the field, and both nymphs and adults were infected with the fungus oil formulation. A total of 1.5 liter oil formulation of fungus was used for 1500 m2. Two methods were used to assess effectiveness: 1) we captured infected insects and fed them fresh grass daily in the laboratory and recorded time to death; 2) we counted insects in the field before and after application. In the field, the number of insects decreased significantly after the fungus treatment. In the laboratory, the lethal time at which 50% of the insects died varied between 8 to 9 days. The effectiveness of M. anisopliae in natural environment decreased with time.