Three species of Entomophthorales were found on adult carrot flies (Psila rosae F.) during two successive seasons:Entomophthora muscae (C.) Fres., Condiobolus apiculatus (Thax.) Remaud. & Keller and Erynia sp. E. muscae was by far the most common species and caused epizootics in one carrot fly population up to 3 times per year. Flies cuaght in the hedge showed a higher infection level than flies caught in the field close to the hedge. Flies caught 200 m away from the hedge showed the lowest infection level. Apparently the hedge was the site of infection, since carrot flies, killed by E. muscae, were found there attached to the underside of the leaves. Flies caught on yellow sticky traps developed only to a limited extend symptoms and gave little information about the fungus infection levels.