Peanut Disease Control Programs and Advisories Begin in Early July

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Programs to prevent and control early (Figure 1) and late leaf spots (Figure 2) will begin soon. In well rotated fields, the first fungicide spray for leaf spot control should be applied when peanuts reach R3. This is when about half the plants in a particular planting have at least one pod starting to develop. Spray programs can be delayed by two weeks (R3+2) on the cultivar Bailey, which has moderate partial resistance to leaf spots. Reapply foliar fungicides every two weeks, or follow the Peanut Leaf Spot Advisory after the first spray.

The North Carolina Peanut Leaf Spot Advisory is a cooperative effort by the State Climate Office of North Carolina and the Department of Plant Pathology at NC State University. The advisory is a safe way to minimize fungicide applications by spraying only when weather conditions favor disease.

We also provide spray advisories to warn growers that weather conditions favor development of Sclerotinia blight (Figure 3). Sprays for Sclerotinia blight control are necessary only in fields with a history of disease. Due to favorable weather in many parts of the state, growers should start scouting for Sclerotinia blight now. Once rows are within 6 inches of closing, follow advisories to determine whether conditions are right for disease development.

early leaf spot

Figure 1. Symptoms of early leaf spot on peanut

Late leaf spot

Figure 2. Late leaf spot. Spots seen on the underside of the leaf are dark brown and may have spores. Note that some spots have halos.

Sclerotinia blight

Figure 3. Sclerotinia blight usually is first seen as fluffy growth on stems, pegs or leaves. Infected areas often are bleached.

Leaf spot and Sclerotinia advisories are delivered by daily emails throughout the summer. Contact Barbara Shew or your County Extension Office if you would like to receive peanut disease advisories. Advisories are also available on-line at http://ncsupeanut.blogspot.com/

For more information about peanut diseases, see 2016 Peanut Information