Knowing the field history is a crucial factor in controlling diseases, especially soil-borne pathogens, in peanuts.

Rotation, scouting, variety selection, proper fungicide use and scheduling protective applications also play important roles, says Oklahoma State University Extension plant pathologist John Damicone.

Damicone reviewed peanut disease control recently at the annual Oklahoma Peanut Expo at the Quartz Mountain Resort near Lone Wolf, Okla.

He said field history is especially important for soil borne disease and nematode infestations. “We are seeing more nematode problems,” he said. “Our best bet has been rotation, two to three years out of any legume crop.”

He also noted that knowing which market types are more susceptible to specific disease organisms helps peanut producers make informed decisions about what to plant where and how to manage runners, Virginias and Spanish varieties.

For the latest on peanut and other crop issues, please check out Southwest Farm Press Daily and receive the latest news right to your inbox.

Leaf spot, for instance, may be hard on Spanish and runner types. Runners are also susceptible to sclerotinia and pod rot. Virginias are vulnerable to pod rot and sclerotinia, particularly with a history of the disease in the field.

A 14-day spray schedule is still routine for leaf spot control, Damicone said. “That’s typically six spray applications. A reduced program of three applications  (climate-based) is a possibility and seems to work best with runner peanuts.”

Controlling early leaf spot is important, he added, to reach high yield goals. “We need to prevent plant defoliation and get into September with leaves intact.”

Fungicides for leaf spot control are preventive, Damicone said. “They work like a coat of paint to protect the leaf against infection. We can’t cure leaf spot. If we wait until we see leaf spot on the plants, we will get damage.”

He said plants may be infected two weeks before symptoms appear.

Weather trends also affect leaf spot occurrence. “In 2013, rainfall was variable across our peanut production area,” Damicone said. “In central and eastern Oklahoma, we had abundant rain and we saw some leaf spot pressure.”

Farmers have several fungicides available for leaf spot including Headline, Bravo, Tilt, Folicur, Provost, Fontelis, Abound, Priaxor, Moncut, Equus and MCW.

“Depending on the product, leaf spot control trials show that  fungicide application resulted in up to a 1,500 pound per acre yield advantage,” Damicone said.