RELATION OF WEATHER VARIABLES TO INCIDENCE OF ZEARALENONE IN CORN IN SOUTHERN ONTARIO

Abstract

Incidence of zearalenone was estimated according to frequency with which the mycotoxin was detected in corn (Zea mays L.) samples received for mycotoxin analyses at the Veterinary Services Laboratory, in Guelph, Ontario. Sampling periods were 1 Sept. to 31 May in 6 successive yr. Frequency of zearalenone was high in 1975–76, moderate in 1972–73, 1976–77 and 1977–78, and low in 1973–74 and 1974–75. Incidence of zearalenone-positive samples for each 10⁴ ha grain corn was highest in a zone extending from the Bruce Peninsula to the Niagara region. Incidence of zearalenone-positive corn samples correlated strongly with rainfall for August, but only moderately or weakly with rainfall for July, September and October. Rain promoted zearalenone accumulation indirectly by favoring epidemic development in corn of the mycotoxigenic fungus Fusarium graminearum. Correlations between zearalenone frequencies and temperatures were weak. Persistent wetness in corn increased ear rot development and incidence of zearalenone.