SEASONAL OCCURRENCE OF A FUNGAL PATHOGEN, NEOZYGITES-ADJARICA (ENTOMOPHTHORALES, NEOZYGITACEAE), INFECTING BANKS GRASS MITES, OLIGONYCHUS-PRATENSIS AND 2-SPOTTED SPIDER-MITES, TETRANYCHUS-URTICAE (ACARI, TETRANYCHIDAE), IN-FIELD CORN

The seasonal occurrence of epizootics caused by the fungus Neozygites adjarica (Tsintsadze & Vartapetov) were studied in populations of Bank s grass mites, Oligonychus pratensis (Banks), and twospotted spider mi tes, Tetranychus urticae Koch, on field corn, Zea mays L. The first ev idence of fungal infection was 5 August, but the major epizootics occu rred 14 August to 8 September. The fungal epizootics followed periods of 8-10 h per day of ambient relative humidity above 80%. N. adjarica epizootics occurred in the four test fields, but it was not clear whet her or not the epizootic was the major agent of spider mite mortality. Predatory arthropods, miticide applications and corn maturity also ap peared to be important spider mite mortality factors. N. adjarica epiz ootics were erratic and occurred too late in the season to prevent spi der mite damage in corn. Awareness of conditions likely to foster fung al epizootics in spider mites will help us understand spider mite popu lation dynamics.