Evaluation of effects of indigenous entomopathogenic fungus, Metarhizium anisopliae (Metsch.) sorokin on on-target organism, The Bombyx mori Lin

Abstract

A laboratory experiment was conducted to evaluate the level of effects by different concentrations of indigenous entomopathogenic fungus, Metarhizium anisopliae (Metsch.) Sorokin spores by dipping the non-target organisms, the silkworm, Bombyx mori L. in the fungus suspension at laboratory condition in Rampur, Chiwan, Nepal. The selected most virulent fungus isolate, among 26 was tested at different concentrations of 107, 106, 105, 104, 103 and 102 number of spores per ml including a control each replicated thrice to each of 30 fourth instar silkworm larvae. The mortality of silkworm larvae due to fungus started only after five days of the treatment and finally caused 70, 44.44, 28.88, 26.66, 23.33 and 3.33 percent death of silkworm larvae with 107, 106, 105, 104, 103 and 102 spores per ml of fungal conidial concentrations respectively. The larval body weight was significantly lower even one day after treatment in the lots treated with 107 spores as compared to other concentrations. On the third and fourth day of treatment, there was no significant difference in the body weight of silkworm larvae in all the treatments. There was significantly lower weight in the lots treated with 107 spores after fifth, sixth and seven days of treatment but after eighth days, there was no significant difference in the body weight with the treatments. The laboratory result indicated that even a small number of conidia of M. anisopliae (Metsch.) Sorokin caused mortality and was found hazardous to silkworms.