Comparative study on the susceptibility of adult Sitophilus granarius (L.) (Coleoptera: Curculionidae) and larval Galleria mellonella (L.) (Lepidoptera: Pyralidae) to the entomogenous fungus Beauveria bassiana (Bals.) Vuill

Using standard laboratory methods, the susceptibility of 3rd instar larvae of Galleria mellonella and adults of Sitophilus granarius to the entomogenous fungus Beauveria bassiana was determined. Conidia of the fungus are the active component of the preparation “Boverosil” registered in Czechoslovakia for the control of residual infestations of pests of stored products in grain stores and silos. Virulence against larvae of G. mellonella was measured as an LC 50 value of 1.14 × 10 8 conidia/ml. At this concentration mortality of S. granarius adults was about 3%. An exact LC 50 value could not be determined accurately for adults of S. granarius, but the LC 50 appeared to range between 2 × 10 8 and 5 × 10 8 conidia/ml. The extent of mortality of S. granarius appeared to be affected by the number of conidia sticking to the insect's body at the start of the test, i.e. during the 2 hr exposure of the insect to the sprayed suspension before mixing with excess grain. During this period the r.h. was 100%, dropping below 90% after mixing, by which time the impact of spore concentration was reduced to a minimum.