Alabama Cotton, Peanuts: 4 Late Season Disease Considerations

Pustules of peanut rust found on the underside of the leaves in the canopy. Photo: Jay Capasso, University of Florida

Late season foliar and soilborne peanut diseases continue to be problem in Alabama due to conducive weather. Peanut rust has been found on non-treated plants in research trials in Headland. This is not surprising given the warm, wet weather and bands of rain from the tropical systems that moved through the area a couple of weeks ago.

Rust is easily identified by the presence of numerous, tiny reddish-orange pustules on the undersides on leaves. The good news is that we are not finding it in treated plots as the disease can be managed with applications of chlorothalonil. We have also continued to see early leaf spot and white mold in peanuts this week.

Producers may be wondering about whether they should put out additional fungicide applications to manage these late season diseases. Here are a few things to consider:

1. If you have 3 weeks to go until you are projected to dig and there is little-to-no disease in the field, then you will not need to put out additional fungicides unless there is threat of a tropical storm or hurricane. Producers should keep an eye on the Gulf this week as Tropical Storm Sally may impact southwestern Alabama from early Tuesday to late Wednesday.

2. If you are more than 3 weeks away from your projected dig, on your last fungicide application, and seeing some leaf spot beginning to develop, then consider applying chlorothalonil (1 pt/A) tank-mixed with tebuconazole (7.2 fl.oz./A), Alto (5 fl.oz./A), or Topsin (2.5 fl.oz./A).

3. If you are on your last spray and very little leaf spot is present, then 1.5 pt/A of chlorothalonil may be all that you need.

4. For fields where white mold is a concern, if white mold is confined to individual plants scattered across the field, then consider adding tebuconazole to your last leaf spot application for some late season “insurance.” However, if the disease is more severe and you are worried about it, then you may want to consider using a more effective product such as Convoy.

When selecting fungicides this late season, please be sure to take their pre-harvest intervals (PHI) into consideration as some products such as Alto or Convoy have a 30- or 40-day PHI, respectively. For additional information and fungicide recommendations, please refer to the ACES Peanut  IPM Guide.

As reported last week, fungal diseases such as target spot, areolate mildew, and boll rots continue to be an issue for Alabama cotton. As a reminder for target spot and areolate mildew, applications of fungicide such as Elatus, Priaxor, and Quadris can provide yield protection if the crop is further than 4 weeks from defoliation and has good yield potential, the disease has not spread too far, and weather favors disease development.

Unfortunately, fungicides do not provide protection against boll rots. Please refer to the ACES Cotton IPM guide for fungicide rates and recommendations.

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