Abstract
The development of eyespot disease of winter wheat by Pseudocercosporella herpotrichoides (Fron) Deighton in a field in Akita, Japan was studied in 1983/84 with snow cover having a depth exceeding 10cm for 12 weeks. Wheat had been continuously grown for 6 years and eyespot disease occurred intensively in the previous growing season in the field. Plants with eyespot lesions in leaf sheaths increased up to 70% by the middle of December, shortly before the start of prolonged snow cover. Conidial dispersal of the pathogen was observed from October to December. The development of the lesion appeared to originate from direct infection of dispersed conidia, and infection of coleoptiles scarcely caused the infection of leaf sheaths. During the period of this cover, eyespot lesions seemed to have increased in size and number per plant and penetrated several inner leaf sheaths. Infection of culms started at 5 weeks following the end of the cover and reached almost all culms infected within the next 6 weeks. It is suggested that most of the infection of culms resulted from the development of the disease originally dispersed to the outermost leaf sheaths before the snow cover.
