Potential Early and Late Pod Set and What That Means For the 2022 Peanut Crop

by T. R. Faske, Extension Plant Pathologist - August 15, 2022

Currently, most of the Arkansas peanut crop is pegging and setting pods (Fig. 1). Hot, dry conditions in July caused some cultivars to cease producing flowers, which may contribute to two distinct pod sets, early and late. If this occurs, farmers will need to decide how long to wait to dig to capture the late crop without losing the early crop to digger loss. Therefore, it will be important to check pod maturity before digging. Most dig when 75% of the pods are brown or black. If farmers decide to wait, late season diseases may be problematic.

Figure 1. Peanut pod set from runner peanut field in early August in northeastern Arkansas (2022).

One of the most important late season diseases in Arkansas is late leaf spot caused by Nothopassalora personata (syn: Cercosporidium personatum). Typically, late leaf spot develops in September in Arkansas, and because most are applying preventative fungicides, it has not been a major issue. Late leaf spot is relatively easy to identify in the field as spots on the lower leaf surface that are typically black in color and may be rough to the touch when spores are being produced (Fig. 2). Black lesions can also be observed on peanut stems and petioles. Significant defoliation by late leaf spot causes the plant to “shut down", which can contribute to weak peg strength and contribute to greater digger loss. Most peanut fungicide programs end with chlorothalonil (Bravo, Equus, Echo), but a rain shower will wash that off the plant. So, consider a systemic fungicide like tebuconazole to provide some systemic protection.  

Figure 2. Late leaf spots on the lower leaf surface are typically black in color and may be rough in texture when spores are produced.

Currently, the most common disease on peanut in Arkansas is southern blight or southern stem rot. It is a soilborne disease caused by Athelia rolfsii (syn:  Sclerotium rolfsii) (Fig. 3). However, it is not as common or severe as in other peanut producing states like Georgia or Alabama. The fungicides applied in July and August target against southern blight, and some farmers are adding a “premium” fungicide in their program for the August timing. A “premium” fungicide is one other than generic tebuconazole, which most choose to use during the cropping season. Applying a fungicide before a light rain can distribute the fungicide near the soil line where this disease starts. In furrow-irrigated fields, some farmers spray at night when the peanut leaves are folded together and thus do not impede fungicides into the lower canopy.  

Figure 3. White hyphae of the southern blight pathogen, Athelia rolfsii, colonizing organic matter on the soil surface and nearby peanut limb.

If you have any questions, please contact me on Twitter at @travisfaske or email at tfaske@uada.edu.