Looking at peanuts in the field and having peanuts checked for maturity, we are seeing more leafspot show up. Some growers have said it literally showed up over night. Most of these peanuts are close to the Florida line. We see late leafspot get on these peanuts many times. Some defoliation has been noted. Here is a picture of late leafspot sporulating on the bottom of the leaf.
Here are some comments on late leafspot from UGA Extension Pathologist Dr. Bob Kemerait from the 2015 Peanut Update:
- Finding some leaf spot in a field at the end of the season is usually not a problem. As long as the diseases are controlled throughout the season, limited defoliation (up to about 30 – 40%) is not likely to affect your yeield. The appearance of leaf spot at the end of the season typically does not mean that your program was ineffective or a failure.
- Some grower in Florida are mixing chlorothalonil with Topson-M or Topsin 4.5F or copper fungicides such as Kocide for their final leaf spot sprays to increase peg strength prior to harvest. What do we recommend in Georgia?
- Combinations of chlorothalonil and Topsin-M currently provide excellent control of leaf spot.
- Combinations of chlorothalonil and copper are also effective in the control of leaf spot.
- Data collected at Clemson University demonstrates that peg strength is not increased with use of Topsin-M, Topsin 4.5F, or copper.
- Failures in leaf spot management in a peanut field are often linked to:
- Unacceptable delays in starting your program.
- Improper calibration of equipment (not enough material applied).
- Unacceptable delays between applications (weather conditions keep growers out of a field).
- Rain events immediately after a fungicide application have washed fungicide away.