Virulence of Some Isolates of Entomopathogenic Fungus, Beauveria bassiana on Ostrinia nubilalis (Lepidoptera: Pyralidae) Larvae

The European Corn Borer (ECB) is one of the most important insect pests of corn and some other crops such as rice in Iran. This pest is one of the most important hosts of the entomopathogenic fungus Beauveria bassiana, a well known fungal entomopathogen with high host range and considerable potential in insect pest control. In an isolate selection program of fungal isolates against ECB, ten isolates consisting of eight isolates from Iran and two from other countries were assayed using the dipping method on third instar larvae of ECB. Inoculum concentrations were ۱۰۴, ۱۰۵, ۱۰۶, ۱۰۷, and ۱۰۸ conidia ml-۱. For each concentration, ۳۰ larvae were dipped into the conidial suspension for ۳۰ secends. Control larvae were treated with distilled water containing ۰.۰۳ percent Tween-۸۰ as surfactant. Each experiment was repeated three times. Results showed that BEH isolate which was isolated from the soil of insects living in the field, caused the highest mortality in larvae in comparison with other isolates with a mean of ۵۷.۶۷ percent mortality using ۱۰۸ conidia ml-۱. Other isolates, such as DEBI۰۰۷ and EVIN I, were scored in the lower position with producing ۵۳.۴۳ and ۴۲.۶۷ percent mortality, respectively. EVIN II, DEBI۰۰۲, and DEBI۰۰۸ caused the lowest mortality in assayed larvae. A decrease in larval feeding was detectable a few days before death. Possible causes for the low mortality in isolates are discussed.

کلیدواژه ها:

Beauveria bassiana ، bioassay ، Entomopathogenic fungi ، Ostrinia nubilalis