STATUS OF CORN DISEASES IN ONTARIO, 2019 CROP SEASON

There were 165 corn fields surveyed in Ontario during the 2019 crop season. The most frequently detected leaf diseases were common rust (135, 82%) and NCLB (112, 68%), and the least was southern rust (11, 7%). Mean severities of 1.8 +/- 0.9, 1.6 +/- 0.8, 1.4 +/- 0.7, 1.2 +/- 0.4, 1.2 +/- 0.3, 1.2 +/- 0.2, 1.2 +/- 0.2, and 1.0 +/- 0.1 were recorded for common rust, northern corn leaf blight (NCLB), grey leaf spot (GLS), northern leaf spot (NLS), eyespot, anthracnose leaf blight (ALB), physoderma brown spot (PBS), and southern rust, respectively. NCLB, GLS, and common rust caused the most damage with severities >= 5 in some of the surveyed fields. Some inbred lines and hybrids with late maturity and exposed ear tips had incidence of common smut ranging from 30-90%. Ear rot was found at much lower levels than previous years, but some inbred lines and hybrids with early to mid- maturity and exposed ear tips had incidences up to 50%. Stalk rots were found in 16 (10%) of surveyed fields, including top-die back (9), pythium stalk rot (6), and fusarium stalk rot (1), with maximum incidence up to 35%. Stewart's bacterial wilt, Goss's bacterial wilt and tar spot were not detected.