Susceptibility of the Red Palm Weevil, Rhynchophorus ferrugineus (Olivier) to the Green Muscardine Fungus, Metarhizium anisopliae (Metsch.) in the Laboratory and in Palm Trees Orchards

The green muscardine fungus, Metarhizium anisopliae (Metsch.) was isolated from naturally infected red palm weevil, Rhynchophorus ferrugineus (Olivier) in Egypt. The isolated fungus was tested in laboratory bioassay experiments against the pest. Three concentrations of the fungus (i.e.10(11), 5x10(10), and 2.5x10(10) spores/ml were applied to both full grown larval and adult stages. Laboratory pathogenicity tests revealed mortality rates of 88.3 +/- 2.3 and 79.3 +/- 0.4 % for larval and adult stages at 10(11) spores/ml concentration, respectively. Mortality rates were 81.6 +/- 2.4 and 72.5 +/- 0.7 % for larval and adult stages, respectively in the case of 5x10(10) spores/ml concentration. The concentration of 25x10(9) spores/ml scored average mortality rates of 69.9 +/- 5.3 and 60.3 +/- 0.7 % for both stages, respectively. Field trials were conducted to test the efficacy of M. anisopliae against R. ferrugineus infestation. Mortality levels of R. ferrugineus stages in the field experiments were represented by the recovery percentage of the infested palm trees (RPIPT). The RPIPT was 58.33, 41.67 and 16.67 % for the tested concentrations, respectively.