Gray Leaf Spot in Corn
Corn Disease Information Note 3
Steve Koenning – Plant Pathology Extension Corn Specialist
Gray leaf spot is caused by the fungus Cercospora zeae-maydis. The fungus survives overwinter in corn debris and may be especially damaging in reduced tillage systems where corn follows corn. Typically, disease is most severe in the mountains and piedmont of North Carolina, but also has caused yield losses in the coastal plain and tidewater regions. High humidity is required for the fungus to infect leaves.
The symptoms of gray leaf spot are rectangular lesions on the leaf surface 1 to 5 mm in width by as much as 6 cm long, that are usually restricted by small leaf veins (Fig. 1). Lesions are yellow to gray, and as they mature the gray lesions remain opaque. The fungus generally produces spores on the underside of the leaf and the spore bearing structures may appear as small black specks. As disease progresses the lesions may coalesce and the entire leaf may turn brown.
Resistance to gray leaf spot is controlled by many genes (polygenic resistance) Hybrids with high levels of resistance to gray leaf spot are available and should be considered in systems using minimal tillage with limited rotation. Because corn hybrids change so frequently, it best to consult with seedsmen for information on hybrid resistance to this and other diseases in high yield environments.
Plant Disease Information Notes Home Page
with a specific problem, contact your local North
Carolina Cooperative Extension Service Office. Outside
North Carolina, look for your state extension service
Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application by growers may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data. All recommendations for pesticide use were legal at the time of publication, but the status of registration and use patterns are subject to change by actions of state and federal regulatory agencies
Published by the North Carolina Cooperative Extension Service Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last update to information: July 2005
Last checked by author: July 2005
Web page last updated on July 2005