[caused by Sclerotinia minor]
Sclerotinia blight has been found in all traditional peanut counties in North Carolina and Virginia. Because this disease starts by killing individual limbs, careful scouting is required to see symptoms when they first appear. Vines must be pulled back to reveal the cottony growth of Sclerotinia on bleached stems. Signs and symptoms are most visible on humid mornings and after a rain. The end portion of infected limbs may remain green and look healthy for several days before wilting is evident. The small black sclerotia resemble mouse or insect droppings and may be seen on and in infected tissues. Disease is favored by cool, wet conditions and is more severe on injured vines.
fluffy fungus growth
bleached and shredded stems
To prevent build-up of damaging levels of Sclerotinia blight, rotate as long as possible with cotton or corn. Canola and several cool-season vegetables are hosts of S. minor and should not be used in rotations. In addition, many common winter annual weeds are hosts. They support reproduction of the fungus during winter fallow, potentially reducing the benefits of rotation. Planting a winter cover crop may reduce populations of the weeds that host the Sclerotinia blight pathogen.
Avoid vine injury by cultivating early (before June 15) or not at all, using small tires, and spraying for leaf spot on the advisory program to minimize trips across the field. Frequent application of the leaf spot fungicide chlorothalonil (Bravo, various brands) can make Sclerotinia blight more difficult to control. The new multiple-disease-resistant cultivar Bailey has much higher resistance to Sclerotinia blight than older, moderately resistant cultivars; avoid susceptible cultivars in fields with a history of disease.
The fungicides fluazinam (Omega) and boscalid (Endura) are effective against Sclerotinia blight when applied preventatively. Fields with a history of serious problems should be scouted carefully beginning when vines are close to touching, or around July 4. Treat when Sclerotinia blight is first observed (on demand) or 60 to 70 days after planting (calendar program) or according to a Sclerotinia blight advisory. If the disease continues to spread, one or two more applications may be made at 3- to 4-week intervals.
irregular shaped “mouse droppings” sclerotia
A weather-based Sclerotinia blight advisory can be used to time applications and prevent unnecessary fungicide applications. Sclerotinia advisories are available by e-mail every day during the growing season in North Carolina. Consult your county agent for more information about Sclerotinia blight advisories or to receive Sclerotinia advisories by e-mail. Sclerotinia advisories for Virginia can be found at http://webipm.ento.vt.edu/cgi-bin/infonet1.cgi
Publication Copyright Information:
© North Carolina State University & Virginia Tech University. 2010. Prepared by Barbara Shew, Bridget Lassiter, and Gail Wilkerson [Departments of Plant Pathology and Crop Science, North Carolina State University, Raleigh, NC] and Pat Phipps [Tidewater Research Station, Virginia Polytechnic Institute and State University, Suffolk VA]. Additional pictures provided by Joyce Hollowell, Brian Royals, Damon Smith, Brenda Watson, Al Cochran, and Craig Ellison.
Text taken from the 2010 NC Peanut Information Guide, (AG 331), North Carolina Cooperative Extension Service, the 2010 Virginia Peanut Production Guide, (432-101), Communications and Marketing, VPI, and the Integrated Pest Management Peanut Scouting Manual, NCSU and VPI.
This publication was made possible through a Crops at Risk (CAR) grant administered by the United States Department of Agriculture (USDA).