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
Newer strains of potato virus Y spread by aphids cause damage to the flesh of the tubers. Photo courtesy Washington State University
Crop Protection
July 18, 2016
Potato Growers: Be On The Lookout For New Strains Of Potato Virus Y
Standard measures have been typically less effective against new strains. Read More
fanned out 100 dollar bills
Citrus
July 18, 2016
Bayer Ups Bid To Buy Monsanto
Reports indicate new offer at nearly $65 billion. Read More
Dickeya early symptoms for web
Crop Protection
July 13, 2016
Dickeya: A New Potato Disease
The disease caused big losses last year; growers need to check fields for symptoms. Read More
Whiteflies on a leaf
Fruits
July 11, 2016
Exotic Whitefly On The Move In Florida
Reports confirm notorious Q-biotype species is now present in eight counties. Read More
(Photo credit: Nancy Bosold, Horticulture Educator, Penn State Extension)
Apples & Pears
July 8, 2016
Spotted Lanternfly Quarantine Expands In Pennsylvania
More townships added as small populations of the pest are found in municipalities adjacent to previously quarantined areas. Read More
potato field
Crop Protection
July 8, 2016
Public Policy Decisions And The Influence Of Dangerous Data [Opinion]
EPA needs to get back to using solid science and avoid bending to popular opinion. Read More
Neoafabraea pathogen on twig lesions at wounds caused by a mechanical harvester on 'Arbosana.' (Photo credit: Flourent Trouillas, University of California)
Disease Control
July 7, 2016
Disease Reportedly Returns To California Olive Orchards
The pathogen, which was originally reported along the coast in 2013, was recently found in the Sacramento Delta area. Read More
The Latest
Crop Protection
July 18, 2016
Early Infection Of Downy Mildew Confirme…
The pathogen has been confirmed in Michigan cucumbers in Bay County for the 2016 season. Read More
Crop Protection
July 18, 2016
Potato Growers: Be On The Lookout For Ne…
Standard measures have been typically less effective against new strains. Read More
Citrus
July 18, 2016
Bayer Ups Bid To Buy Monsanto
Reports indicate new offer at nearly $65 billion. Read More
Crop Protection
July 13, 2016
Dickeya: A New Potato Disease
The disease caused big losses last year; growers need to check fields for symptoms. Read More
Crop Protection
July 8, 2016
Public Policy Decisions And The Influenc…
EPA needs to get back to using solid science and avoid bending to popular opinion. Read More
Crop Protection
July 6, 2016
Abiotic Issues Affect Vegetable Producti…
Although most issues you face are biotic, abiotic issues can greatly impact vegetable crop yield and quality. Read More
Crop Protection
July 6, 2016
Crop Production High Tunnel iBook Now Av…
The book is designed to help growers who are beginning high tunnel production. Read More
Crop Protection
June 23, 2016
Scientists Selected To Work On Healthy H…
The four-year, $1 million program has a goal of improving the health of honeybee colonies. Read More
Crop Protection
June 15, 2016
Robotic Weeder Makes Its Debut
Developed in France, the autonomous, electric-powered, lightweight machine doesn’t compact soil and operates for up to eight hours. Read More
Citrus
June 14, 2016
Monsanto Rejects Second Bid From Bayer
Wall Street Journal reports Monsanto seeks bid increase from Bayer. Read More
Crop Protection
June 6, 2016
Bayer Teams Up With Aerospace Company To…
Collaboration with Planetary Resources is designed to arm growers with information to save water, etc. Read More
Crop Protection
June 6, 2016
Tessenderlo Kerley Opens Research And In…
Farm will allow company’s Crop Vitality division to try out materials under real world conditions. Read More
Crop Protection
June 5, 2016
How To Manage Consperse Stink Bug In Tom…
Tips to control the pest include pheromone traps, sanitation, and site selection. Read More
Crop Protection
June 3, 2016
Stockton Group Puts Stock In Crop Protec…
Industry veteran hired to help bolster global biopesticide business. Read More
Citrus
June 1, 2016
Groups Make Push To Challenge DuPont, Do…
Letter from industry organizations say proposed merger could hinder innovation, raise prices, and reduce choices. Read More
Crop Protection
June 1, 2016
5 Major GMO Myths Debunked
Disproving the myths associated with the technology and highlighting lesser-known truths may help improve public reception. Read More
Crop Protection
May 31, 2016
Study: Honeybees Collect Urban Pesticide…
Purdue research indicates pollen is consistently contaminated with not only agricultural, but urban pesticides. Read More
Crop Protection
May 31, 2016
A Preventive Approach Reduces Infection …
Conditions favoring disease development and spread have led to the establishment of early warning or forecast programs for late blight and early blight. Read More
[gravityform id="62" title="false" description="false"]