Early Season Disease Management With the crop moving beyond seedling stage, it is time to think about common fungal pathogens.
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reseason decisions, such as varietal selection and in-furrow applications, have been made, and peanuts are in the ground starting to grow. Decisions for management of tomato spotted wilt and nematodes are mostly done. Now it is time to think about early season disease management options for common fungal pathogens — peanut rust, leaf spot diseases and white mold/stem rot, and in preparation for next year, Aspergillus and Rhizoctonia.
N. DUFAULT, UF/IFAS
Peanut Rust We saw a reemergence of peanut rust during the 2020 season, which may have this disease on many producers’ minds in 2021. Peanut rust can be a devastating if left unchecked, but luckily many of our leaf spot fungicides also manage this disease. Typically, we do not need to concern ourselves with rust early in the season, as this disease is generally spread from more tropical climates where volunteer hosts are abundant. This means it takes some time for rust to appear in our peanut fields. This was the case last year when it began to be identified in late August and early September. The primary concern with peanut rust early in the season is in terms of scouting for this disease and monitoring the crop for any early introductions. More information about peanut rust can be found in the article, “The What, When and How of Florida’s Peanut Rust Issue” on the Panhandle Ag News website at http://nwdistrict.ifas.ufl.edu/phag/.
N. DUFAULT, UF/IFAS
Know the difference between late and early leaf spot symptoms, which are caused by two different pathogens.
This picture shows peanut rust pustules on the underside of a leaf.
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THE PEANUT GROWER • JUNE 2021
Leaf Spot Diseases Peanut leaf spot diseases are an annual problem for producers. These leaf spot diseases are caused by two different pathogens, both of which tend to show up every year in varying amounts. Typically, we see more early leaf spot in the Suwannee Valley and more late leaf spot in the Florida Panhandle. However, it is not uncommon to have different leaf spot pathogens in neighboring fields. This means we need to have a good mixture of fungicide products in our programs, as our generic products, such as tebuconazole, azoxystrobin and pyraclostrobin, all vary in how they manage each pathogen. The most often asked question related to peanut leaf spot disease management is, “When do I pull the trigger and apply my first spray?” There is no simple answer to this question. Leaf spot disease onset can occur anytime between 25 and 90 days after planting. However, if we are looking to delay our first fungicide application, then we must focus on reducing our risk for leaf spot disease as much as possible. Peanut Rx is an excellent tool to provide insights related to risk reduction. Typically, leaf spot disease quantity, as well as onset, depends on variety, crop rotation, in-furrow treatments and the timely application of fungicides. Having a resistant variety in a well-rotated field, three or more years away from PEANUTGROWER.COM
