AEROBIOLOGY OF CLAVICEPS-PURPUREA IN KENTUCKY BLUEGRASS

Airborne ascospores of Claviceps purpurea were monitored with volumetr ic spore traps in two fields of Kentucky bluegrass in Oregon during 19 89 and 1990. A diurnal periodicity in ascospore release was observed, with peak catches between 1:00 and 6:00 a.m. Sporulation events (one o r more consecutive days on which ascospores were trapped) generally be gan 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, a scospore release increased with rise in temperature from 5 to 20 C.