Relationship between climatic factors and eyespot of winter wheat and timing of fungicide applications in Hokkaido

Abstract

Influence of climatic factors on eyespot disease of winter wheat was investigated in Hokkaido from 1987 to 1996. Disease severity was associated negatively with the lowest temperature in early May and positively with the number of days with precipitation above 1 mm in early November. The development of eyespot disease was examined for 2 years. Lesions were first observed in late October, and incidence rate increased sharply after late April. We consider that rainfall in early November promoted primary infection, and the low temperature in early May extended the infection period. The control effects of thiophanate-methyl and prochloraz were examined in different growth stages of winter wheat for 3 years. Early May (GS 31) was the most effective, followed by late April (GS30) and mid-May (GS 33). This study suggested that disease severity of eyespot disease can be predicted from climatic factors to determine the necessity of control.