Mortality of the Western corn rootworm, Diabrotica virgifera virgifera larvae caused by entomopathogenic fungi

Mortality of the Western corn rootworm (WCR) larvae caused by entomopathogenic fungi Beauveria bassiana, Beauveria brongniartii, Metarhizium anisopliae was investigated in a laboratory. Larvae were treated with a spore suspension (concentration of 2.0 x 107 conidia/ml) by immersion. Only one strain of entomopathogenic fungi, a strain of B. brongniartii, significantly influenced mortality of WCR larvae after 7 days. Average mortality of the larvae was 17.63%. After 14 days, five strains of B. bassiana, two strains of B. brongniartii and one strain of M. anisopliae significantly influenced mortality of WCR larvae, with average mortality ranging from 25.83% to 60.57%. After 21 days from exposure of the larvae to spores, four strains of B. bassiana, two strains of B. brongniartii and one strain of M. anisopliae significantly influenced mortality of the WCR larvae with average mortality ranging from 62.5% to 86.6%. Results confirmed that interaction is possible between fungal strains and insect of a various geographical provenance. More than half of the tested fungal strains significantly influenced the mortality of WCR larvae after 14 and 21 days. We found that differences between strains were more important than differences between fungal species.