AEROBIOLOGY OF CLAVICEPS-PURPUREA IN KENTUCKY BLUEGRASS

Airborne ascospores of Claviceps purpurea were monitored with volumetric spore traps in two fields of Kentucky bluegrass in Oregon during 1989 and 1990. A diurnal periodicity in ascospore release was observed, with peak catches between 1:00 and 6:00 a.m. Sporulation events (one or more consecutive days on which ascospores were trapped) generally began 2-3 days after rain and continued for 1-16 days. Cumulative number of ascospores trapped paralleled cumulative hours per day with rain. Ascospore release in the field was not correlated with temperature or relative humidity. Under controlled temperature conditions, however, ascospore release increased with rise in temperature from 5 to 20 C.