Effects of fungicide timing on the severity of eyespot on winter wheat or winter barley inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides

Abstract

Plots of winter wheat or winter barley inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides were sprayed with carbendazim plus prochloraz either at growth stage (GS) 30/31, or at GS 33/39 (wheat) or at GS 51 (barley). At GS 30/31 > 75% of the shoots of both wheat and barley had eyespot lesions in 1986 and 1987 and there were, on average, < 2 leaf sheaths left to penetrate before the fungus reached the stem. In 1988, the incidence of eyespot was 10–50% at GS 30/31 and there were three leaf sheaths left to penetrate. Spray treatments generally reduced the severity of eyespot lesions on stems at GS 83 in both W-type and R-type plots of wheat and barley. The early spray treatment (GS 30/31) generally controlled eyespot better than the late treatment in both W-type and R-type plots. Spray treatments often increased yield, but differences in yield responses were not clearly related to differences in control of eyespot.