What You Need To Know About Northern Corn Leaf Blight

Photo by Margaret McGrath
Photo by Margaret McGrath

Disease Specs

Northern corn leaf blight, caused by the fungus Exserohilum turcicum, was one of the most important sweet corn diseases in South Florida causing significant losses some years. It is still a potential threat, occurring every spring and occasionally late fall. Resistant
varieties have helped reduce impact of the disease in recent times.

Identification

Initial symptoms of the northern corn leaf blight (NCLB) include yellow spots that develop on the foliage. These enlarge to form tan or straw-colored dead areas about four to six inches long and one-half inch wide. NCLB produces a long, elliptical lesion, while those of southern corn leaf spot tend to be oblong and much smaller than those produced by NCLB. Southern blight lesions also are lighter in color (light tan to brown), and have parallel sides rather than the tapering sides of lesions caused by E. turcicum.
NCLB moves from the lower canopy to the upper canopy. Fungal sporulation may be observed with a hand lens on foliar lesions following periods of high humidity. When severe, lesions may become so numerous that they coalesce and turn the entire leaf necrotic.

Survival And Spread

Sources of spores include volunteer corn, debris on the soil from previous crops, seed, and nearby corn plantings. Spores, which may be carried long distances, are spread by rain and wind. Lesions can produce spores in as little as one week, allowing NCLB to spread much faster than many other corn leaf diseases.
Disease development is favored by heavy dews, frequent showers, high humidity, and moderate temperatures. Infection occurs when free water is present on the leaf surface for six to 18 hours and temperatures are 65°F to 80°F.
Infections generally begin on lower leaves and progress up the plant, but infections may begin in the upper plant canopy when spore loads are high.

Management Methods

Although some control can be reducing inoculum through the use of crop rotation and deep plowing of old crop debris, control is best achieved with resistant varieties. Resistant varieties are available and should be considered, particularly for spring plantings.
Fungicide application can effectively control E. turcicum when applied at the right time. Fungicide should be applied when lesions first become visible on the lower leaves or when disease is reported to be in the area. Threat is highest from mid-February into April, but it may be seen during the fall as well.
Triazoles and strobilurins both provide control, with some pre-mixes giving superior control. These products should be used with a broad-spectrum protectant to minimize development of fungal resistance.

Use ethylenebisdithiocarbamate fungicides such as mancozeb as a protectant before disease is present. Apply four to six sprays on a five-to-seven-day basis. Use a surfactant/sticker as corn leaves are waxy and spray tends to run off. Rotate with a stobulurin like Headline (pyraclostrobin, BASF). As corn matures or disease becomes present, rotate between triazoles such as Folicur (tebuconazole, Bayer Crop Science), Monsoon (tebuconazole, Loveland Products), Propimax (propiconazole, Dow AgroSciences), and strobilurins or premixes of the two.

Topics: , , , ,

Leave a Reply

Crop Protection Stories
Bill Stoneman
Crop ProtectionFormer BPIA Head Relishes Challenge Of New Consulting Role
July 28, 2015
JET Harvest Solutions taps Bill Stoneman for his bounty of biocontrol experience. Read More
Late blight shown in a tomato
Disease ControlLate Blight Identified In Indiana, Michigan
July 28, 2015
A potato field in Michigan and a potato and tomato field in Indiana have documented the disease. Read More
UF/IFAS researcher looks after pigs on weed control duty
More VegetablesGot Weeds? Perhaps Pigs Can Help
July 27, 2015
Old-time crop protection method using hogs now being tested by UF/IFAS researchers. Read More
downy mildew symptoms on basil
Disease ControlRed Lights Slow Down Growth Of Downy Mildew On Basil
July 22, 2015
University of Florida scientists say the technology may help growers manage the disease and reduce chemical inputs. Read More
Bacterial wilt of curcurbits
CucurbitsWin The War Against Bacterial Wilt Of Cucurbits
July 22, 2015
Learn how to identify, the survival and spread, as well as management methods of this vegetable disease. Read More
Crop ProtectionRegional Integrated Pest Management Grants Reduced Pest Risks In The West
July 22, 2015
The program created tools and training information designed for Western growers. Read More
Disease ControlStone Fruit Rots Rampant In East
July 21, 2015
The incidents of fruit rots in both sweet and tart cherries and peaches and nectarines are quite high in Pennsylvania Read More
The Latest
Crop ProtectionResources For Knowing Your Soil
July 30, 2015
Getting to know your soil and learning other environmental and natural resources data can be downloaded and is available for use with many computer software platforms for general resource analysis and farm management. Read More
Crop ProtectionNew Fungicide Targets Key Diseases
July 30, 2015
This disease control tool hits two different parts of the fungal life cycle. Read More
Bill Stoneman
Crop ProtectionFormer BPIA Head Relishes Challenge Of New Consulting R…
July 28, 2015
JET Harvest Solutions taps Bill Stoneman for his bounty of biocontrol experience. Read More
Crop ProtectionRegional Integrated Pest Management Grants Reduced Pest…
July 22, 2015
The program created tools and training information designed for Western growers. Read More
Crop ProtectionClue Into Chemigation Best Practices
July 15, 2015
Monitoring performance and quick repairs are critical to successful applications. Read More
Crop ProtectionNew Egg Cage System Could Increase Ladybug’s Bioc…
July 13, 2015
A specialized insect cage system developed by USDA scientists could improve the prospects of mass rearing the pink spotted lady Read More
Crop ProtectionIR-4 Call For Nominations For “SOAR” Award
July 10, 2015
The IR-4 Project, a resource that supplies pest management tools for specialty crop growers by developing research data to support Read More
Crop ProtectionEarly Blight And Septoria Leaf Spot Rampant On Pennsylv…
July 8, 2015
According to a news release from Penn State University, early blight and Septoria leaf spot are present in Pennsylvania tomato Read More
Crop ProtectionDowny Mildew Reported In Ohio Cucumber Fields
July 8, 2015
According to a disease update from Ohio State University Extension, downy mildew was reported in cucumbers on farms in West Read More
Crop ProtectionZeal SC Miticide Now Registered With Liquid Formulation
June 26, 2015
Valent U.S.A. Corporation announced that Zeal SC Miticide has been registered by the EPA with a new liquid formulation that Read More
Crop ProtectionStay A Step Ahead Of Weeds
June 26, 2015
Weed control can be a tricky and costly task made all the more difficult by herbicide resistance and the push Read More
money down the drain
CitrusGovernor’s Budget Veto Likely To Shutter UF/IFAS …
June 25, 2015
A $180,000 increase, plus another $720,000 in funding for program gone in the stroke of a pen. Read More
Crop ProtectionDowny Mildew Makes Early Appearance In Michigan Cucumbe…
June 23, 2015
An alert sent by Michigan State University (MSU) Extension confirms the presence of downy mildew on cucumber leaves in Michigan. Read More
BerriesCaptan Gold 4L Fungicide Now Registered In California
June 16, 2015
ADAMA has received EPA approval for Captan Gold 4L liquid fungicide for use on strawberries, tree fruits, and other specialty Read More
infrared image showing the difference between using crop termination fumigation in the field and not
Crop ProtectionMaximizing Nematode Management In Vegetables
June 12, 2015
Crop termination is the foundation of mitigating the soil pests for the following season. Read More
Crop ProtectionNew Chart Helps Growers Choose The Best Cover Crop
June 9, 2015
USDA scientists have developed a Cover Crop Chart that helps growers determine the best cover crop to meet their management Read More
Bagrada bug
Crop ProtectionBagrada Bug Has The Potential To Spread Throughout The …
June 9, 2015
The bagrada bug has moved into South Texas and has the potential to move to other areas of the U.S., Read More
Guava Fruit Fly specimen
CitrusLos Angeles County Under Quarantine Following Guava Fru…
June 9, 2015
A portion of Los Angeles County has been placed under quarantine for the guava fruit fly (GFF) following the detection Read More