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Crucial factors for peanut disease management

A combination of proper rotation, site selection, variety choices and fungicide treatments decreases potential for yield-robbing foliar and soil-borne diseases in peanuts.

“It’s important to identify the diseases so you can target control measures,” said John Damicone, Oklahoma State University Extension plant pathologist, at the Oklahoma Peanut Expo at Lone Wolf.

“Site selection is important for disease and nematode management,” Damicone said. “We see more nematode infestations every year. A two-year rotation program helps.”

He said applying Temik at planting may reduce nematode damage.

Leafspot control requires preventive fungicide applications, but the number of treatments may be reduced by following an Early Leafspot Advisory Program (MESONET) available online at no charge:

Otherwise, Oklahoma recommendations call for an initial fungicide application 30 to 45 days after planting and then applications on a 14-day schedule throughout the growing season. The advisory program may eliminate some of those in-season applications.

Damicone said using the calendar to time sprays is very effective, but growers sometimes may apply treatments they don’t need. The advisory program permits producers to apply fungicides only when weather conditions favor leafspot development.

He said the advisory program has been used extensively and effectively in Oklahoma. “Strict adherence to risk management rules is required to assure success.”

Damicone said Spanish and Virginia type peanuts are prone to leafspot infections earlier than runner type varieties. “Rotation plays a role."

Fungicide application also reduces crop loss. Yield advantage from leafspot control may be as high as 600 pounds per acre for Spanish and 500 pounds per acre for runners.

Damicone said fungicides protect plants from pathogens, but don’t cure them once the disease is contracted. “Fungicides last 14 days and they must be preventive.”

He said farmers may follow a full calendar spray application approach, starting about 30 days after planting and continuing through September or shortening the treatment window. “The reduced calendar approach works well."

Weather is always a factor. “Moisture equals leafspot weather."

Damicone said several fungicides work well on leafspot, including Bravo, Headline, Elast and Eminent.

He encouraged peanut farmers to keep “an eye out for soil-borne diseases. Pay attention to field history. Variety selection, field history and fungicide selection are all important.”

He said Virginia peanuts are vulnerable to pod rot. “OL02 and OL07 have pretty good tolerance.”

Fungicide options include Folicur, which Damicone says is “dirt cheap,” Provost, Abound, and Headline. Typical target period for soil-borne diseases is July through September. Foliar disease range runs from June through September.

“Controlling soil-borne diseases results in a good yield increase,” Damicone said, “but control costs are high.”

He said sclerotinia blight has become a significant problem in some areas, but growers have “hope with new varieties and chemistry.” Variety recommendations include Tamspan 90, Tamnut OL06, Olin, Tamrun OL07 and Tamrun OL02.

Fungicide options include Endura and Omega. “Both work well.”

Damicone said 2009 was a particularly bad year for sclerotinia. “Yields and grades were down. We had more sclerotinia. A lot of varieties had sclerotinia infections last year. It came in late, in mid-September to mid-October. Without a fungicide spray, no varieties did well.”

Omega treatments made good yields. “Endura was an economical treatment and got leafspot, too. Two shots of Endura at 8 ounces per acre was the best option.”

He said farmers felt “frustrated trying to determine the best time to spray for sclerotinia.”

Damicone said peanut farmers should check their crop in season to determine disease presence, “so they can target sprays.”

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TAGS: Peanuts
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