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
Citrus
July 12, 2017
USDA Pulls 8 Products from Approved Organic Production List
After a few months of speculation, the USDA's Agricultural Marketing Service has published its Sunset 2017 final rule on approved products for organic production and handling. Read More
darkwinged fungus gnat larvae
Fruits
July 12, 2017
How to Deal with Annoying Fungus Gnats on the Farm
Learn how to identify, the survival and spread, as well as management methods for this insect pest. Read More
Close-up of mature diamondback moth
Insect Control
July 7, 2017
Can Genetic Engineering Put an End to Diamondback Moth Plague?
USDA OKs field release of pest with self-limiting gene at Cornell research farm. Read More
Center pivot irrigation system at Florida research farm
Citrus
June 30, 2017
New Project to Promote Water Security for Florida and Georgia Farmers
With the help of five-year, $5 million USDA grant, stakeholders will learn what it takes to better preserve precious resource. Read More
Crop Protection
June 25, 2017
Study Suggests Closer-Proximity Lures Help Increase Insect Pest Catches
Research shows single-trap locations are not as effective as those kept close together. Read More
Mobile technology farming
Citrus
June 22, 2017
Technology Boom Boosting Farm Life to a New Level [Opinion]
Whether it is human genetics or genetics applied to plants, knowledge is growing at a dizzying pace. Read More
Crop Protection
June 21, 2017
Certis Bolsters Biopesticide Business Portfolio with Acquisition
Addition of LAM International to allow for expansion of product development. Read More
Crop Protection
June 21, 2017
Early-Season Scouting Tips for Sweet Corn Growers
Black cutworm and true armyworm have been caught in relatively high numbers across the Midwest, including Michigan. Learn more about determining risk and scouting in your sweet corn plantings. Read More
Cucurbit leaf crumple virus
Cucurbits
June 20, 2017
Take Caution to Curb Cucurbit Leaf Crumple Virus
Learn how to identify, the survival and spread, as well as management methods for this disease. Read More
Purple nutsedge on tomato plants
Fruits
June 16, 2017
Florida Farmers Fighting to Find Their Way out of the Weeds
For growers in the Sunshine State, the battle with pesky plants out of place never ends. Read More
Illustration of CRISPR-Cas9
Citrus
June 15, 2017
Make Way for Life-Saving Science on Your Farm [opinion]
While nature always finds a way to adapt, science continues to find other ways to cope. Read More
Crop Protection
June 12, 2017
Registration Open for Ag Innovations Conference
Event focuses on microbial control strategies. Read More
Berries
June 10, 2017
Orange Rust Management Tips for Brambles
Disease is on the rise this season and can affect any propagated plant material. Read More
Crop Protection
June 7, 2017
Field Scouting Guide for Squash Powdery Mildew
Learn how to spot and treat a pest that impacts all cucurbits. Read More
Purple nutsedge on tomato plants
Cucurbits
June 6, 2017
Scientists Zone in on Precision Weed Control
Surgically placed fumigants at the base of promising pest management method for vegetable growers. Read More
The Latest
Crop Protection
July 23, 2017
USDA Invests $7.6 Million toward Benefic…
Projects to promote beneficial organisms as part of a pest control strategy. Read More
Citrus
July 12, 2017
Tomato Pests Can Be Induced to Cannibali…
The University of Wisconsin's John Orrock says when beet armyworms are exposed to concentrations of methyl jasmonate, they will abandon eating tomatoes — and start eating one another. Read More
Citrus
July 12, 2017
USDA Pulls 8 Products from Approved Orga…
After a few months of speculation, the USDA's Agricultural Marketing Service has published its Sunset 2017 final rule on approved products for organic production and handling. Read More
Crop Protection
June 25, 2017
Study Suggests Closer-Proximity Lures He…
Research shows single-trap locations are not as effective as those kept close together. Read More
Citrus
June 22, 2017
Technology Boom Boosting Farm Life to a …
Whether it is human genetics or genetics applied to plants, knowledge is growing at a dizzying pace. Read More
Crop Protection
June 21, 2017
Certis Bolsters Biopesticide Business Po…
Addition of LAM International to allow for expansion of product development. Read More
Crop Protection
June 21, 2017
Early-Season Scouting Tips for Sweet Cor…
Black cutworm and true armyworm have been caught in relatively high numbers across the Midwest, including Michigan. Learn more about determining risk and scouting in your sweet corn plantings. Read More
Citrus
June 15, 2017
Make Way for Life-Saving Science on Your…
While nature always finds a way to adapt, science continues to find other ways to cope. Read More
Crop Protection
June 12, 2017
Registration Open for Ag Innovations Con…
Event focuses on microbial control strategies. Read More
Crop Protection
June 7, 2017
Field Scouting Guide for Squash Powdery …
Learn how to spot and treat a pest that impacts all cucurbits. Read More
Crop Protection
June 1, 2017
Can Attract-and-Kill Technology Protect …
Since devastating many Mid-Atlantic farms in 2010, this Asian-borne pest continues to cause growers significant headaches. New research, however, may offer insights into treatment options that minimize the use of harsh chemicals. Read More
Crop Protection
May 23, 2017
Valent Grants Organic Farming Scholarshi…
University of Florida Doctor of Plant Medicine student receives $1,500 toward the development of training materials. Read More
Berries
May 15, 2017
Grower Comments on Pyrethroids Being Sou…
Comment period on popular class of insecticides opens today. Read More
Crop Protection
May 14, 2017
Springtail Is an Unexpected Vegetable Pe…
One springtail species is targeting germinating seeds, impacting seedling growth. Read More
Citrus
May 9, 2017
Barn Owls Can be an Effective Control fo…
The predators are already getting results in vineyards and orchards. Research is showing they’re just as effective in vegetable and fruit fields. Read More
Crop Protection
April 30, 2017
BASF Adds Pest, Crop, Weather Modeling t…
ZedX’s agronomic models help farmers make better production decisions. Read More
Crop Protection
April 29, 2017
BioSafe Systems Introduces Broad-Spectru…
Alternative to potassium bicarbonate and lime sulfur for tree and vine crops. Read More
Crop Protection
April 26, 2017
A Guide to Experts Tips on Vegetable Ins…
Here's a resource to quickly reach advice on how to handle insect pests in most regions of the U.S. Read More