Bioassays with dry conidia of isolates of the entomopathogenic fungusBeauveria bassiana (Bals.) Vuill. against Rhyzopertha dominica (F.)(Coleoptera: Bostrychidae)

Abstract: An investigation with thirteen isolates of the entomopathogenic fungus Beauveriabassiana (Bals.) Vuillemin was carried out against adults of Rhyzopertha dominica (F.)(Coleoptera: Bostrychidae) with a goal to estimate the virulence of the isolates using dry conidia(108 conidia/mg) for the treatment. Insects were treated by contact with 1 mg of dry conidiamixed with crumbled wheat grains. Lethal effect of the isolates was evaluated as percentages ofcumulative daily mortality due to mycosis. Virulence of each fungal isolate was estimated byvalues of the median lethal time (LT50), calculated by log probit analysis. The highest lethaleffect (90%) was established in the variant with the isolate 559 of B. bassiana on the 7th day andit attained to 100% on the 10th day after the treatment. The isolate 513 of B. bassiana causedmycosis to adults of R. dominica with less lethal effect – 65% on the 10th day and 80% on the14th day. All other examined isolates caused