Importance of sub optimal temperatures for the virulence of different geographical provenances of entomopathogenic fungus Verticillium lecanii (Zimm.) Viegas.

The virulence of the tested strains was developed from environmental conditions. The strain V24 had a stable virulence at all temperature levels and achieved in relation to the other examined strains the highest mortality of infected insects. The other strains have shown different changes of effectiveness at the sub optimal conditions. Germination of blastospores was temperature depending and correlated in the mostly cases with the virulence.