Production of spores by Cercosporella herpotrichoides

Eyespot lesions on young wheat plants in the field regularly produced conidia of Cercosporella herpotrichoides Fron in early spring. Conidia were not produced on mature growing plants, but after ploughing, lesions on infected straws spored freely, especially in wet weather. In the laboratory, eyespot lesions on straws produced spores when soaked in water for 24 hr., drained and kept continuously wet. Disks 5 mm. diameter, cut from cultures on potato dextrose agar or water agar, produced spores abundantly when kept touching water at favourable temperatures, but excess water reduced sporing. Spores developed most abundantly when temperatures fluctuated between −3 and 13° C., were produced freely when temperatures fluctuated between 12 and 22° C., more slowly at 1–2° C. and were not produced at 24–25° C. Daylight did not seem to influence spore production.