Barry Tillman, UF/IFAS Peanut Breeder, Nick Dufault, UF/IFAS Extension Crop Pathologist., Ian Small, UF/IFAS Crop Pathologist, Ethan Carter, Regional Crop IPM Agent, and Mark Mauldin, UF/IFAS Extension Washington County.
Early Leaf Spot in Peanut

Figure 1. Symptoms of Early Leaf Spot on peanuts in Jackson County in late July 2023. Credit: Barry Tillman, UF/IFAS

This week, (July 24 and July 27) Early Leaf Spot (ELS) was identified in commercial fields in two Florida Panhandle Counties.  In the Panhandle, we usually battle Late Leaf Spot (LLS), that begins to show up in late August or early September.  It is unwelcome news that we have ELS defoliating peanuts in late July with so much of the season remaining. And that means that extra vigilance should be taken in scouting fields, because the upper canopy can look fine while the lower canopy is defoliating.  ELS is characterized by light brown spots, often with a yellow halo (but not always), and significant defoliation especially in the lower canopy (Figure 1).   Under a microscope, the sporulating structures are visible (Figure 2).


Microscopic view of Early Leaf Spot in Peanut

Figure 2. A microscopic view (32X magnification) of the upper surface of a leaf spot of peanut showing the sporulating structures of the fungus that causes Early Leaf Spot. Jackson County, FL, July, 2023. Credit: Barry Tillman, UF/IFAS

We are still a long ways from optimal harvest maturity, even for April-planted peanuts, so it is important to scout your fields and stay on top of leaf spot sprays with quality fungicide programs. Luckily, there are many fungicides available to manage leaf spot pathogens, however, their efficacy can vary for Early (ELS) or Late Leaf Spot (LLS). This means having two quality fungicides in a spray is a must when managing these pathogens. Generic fungicide products such as azoxystrobin and pyraclostrobin have been observed to have reduced efficacy when it comes to managing ELS, while both chlorothalonil and tebuconazole continue to be effective against this disease (Update on 2014 Peanut Leaf Spot Fungicide Trials). The addition of some sulfur formulations has improved azoxystrobin, pyraclostrobin, and tebuconazole products efficacy when managing peanut leaf spots. We have observed in on-farm and small plot research trials that Provost Silver® can be very effective against ELS with Lucento® and Provysol® mixed, with tebuconazole also providing quality management of this disease. When using other leaf spot fungicide products, it is important to consider adding/mixing chlorothalonil or mancozeb into the spray tank, especially when the leaf spot disease is present.

There are many other efficacious leaf spot products and product combinations available to manage these diseases, and the information presented here does not include all possible fungicide products available to manage ELS and LLS of peanuts. Further information on all the products can be obtained from your local UF/IFAS Extension Agent.

For specific peanut disease and fungicide options, use the following publication link:
2023 UGA Peanut Disease Control Options