As cotton and peanut producers begin to plan their defoliation and digging dates, diseases continue to be active in Alabama. In peanuts, early and late spots and white mold continue to be a problem in many fields as conditions continue to favor disease. Leaf spot diseases can severely defoliate peanuts if not controlled.
In cotton, target spot and areolate mildew can also result in premature defoliation and can cause yield losses. At this point in the season, you may be questioning whether you need to apply fungicides to manage these diseases or not.
In peanuts, many producers are close to digging and may not need a fungicide application or may be at their final fungicide application. 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.
2. If you are more than 2-3 weeks away from your projected dig and are:
- Seeing some leaf spot beginning to develop (<25%), then consider applying chlorothalonil (1.0 to 1.5 pt/A) tank-mixed with tebuconazole (7.2 fl.oz./A), Alto (5.5 fl.oz./A), or Topsin (10.0 fl.oz./A).
- On 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.
- The peanuts are 50% or more defoliated from leaf spot, another fungicide application will not be beneficial. Instead focus on selecting a dig date sooner rather than later.
3. If you are on your last spray and white mold is a concern, then you may want to consider adding a white mold fungicide to your last leaf spot application for some late season insurance. If white mold is confined to individual plants scattered across the field, then consider adding tebuconazole.
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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 or Excalia. However, please be sure to check their pre-harvest intervals (PHI) and take them into consideration as some products such as Alto or Convoy and Excalia have a 30- or 40-day PHI, respectively.
In cotton, it all depends on when you plan to defoliate and disease severity (i.e., premature defoliation). Here are a few things to consider:
1. If you are more than 4 weeks from defoliating and the crop has good yield potential and target spot (<25% defoliation) and areolate mildew are already present or conditions remain conducive to disease development, then you should consider making a fungicide application.
2. If you are within 4 weeks of defoliation or disease has already resulted in more than 25% premature defoliation, then I would not recommend applying a fungicide. Target spot can be difficult to control with fungicides if 25 to 30 percent of the leaves are already gone.