“If you can take some defoliation, we have data that shows top yields can still be achieved,” he says. However, if a producer is trying to stretch a 14-day interval out, and then it rains, and the interval becomes much longer, that’s when leaf spot takes hold. “It’s all about what you are comfortable with as a producer,” Kemerait says. “Not every field will work with extended interval applications. These days you also need to consider that fungicide applications do not stop at 120 days. “A perfect storm situation is uncooperative weather, short rotations, overreliance on the same class of fungicides and stretching the intervals of fungicide programs,” he says. “We can manage all of that by being careful with what we do.” Overreliance On SDHIs Kemerait says producers have an expanding arsenal of fungicides; however, with all these new fungicides, there are not any new classes of chemistry.
“Whether it’s Excalia, Provysol, Sipcam — yes, there are different chemistries, but they are all the same class — the succinate-dehydrogenase-inhibitors, or SDHI class, as they are most often called. “We are becoming increasingly familiar with and reliant on these fungicides,” he says. “And I’ll even use the term ‘overreliant’ because I think if you take shorter rotations and weather, and you rely on a single class of chemistry to carry the lot, bad things can happen. In 2021, with the rain, we saw a lot of leaf spot.” Kemerait says no matter the cost, fungicides are needed to fight disease, but be careful to not rely too heavily on the SDHIs. “If you don’t incorporate other chemistries, resistance will develop.” The addition of sulfur as a tank-mix partner can help with leaf spot control. However, Kemerait says certain sulfur products should be used. “Products that offer additional leaf spot protection include Microthiol 80W, Drexel Sulfur 80W, Drexel Suffa 6F,
TechnoS 90W and Accoidal 80WG.” White Mold Still Garners Attention Although leaf spot is the disease causing more problems in producers’ fields, some years ago it was white mold. Tim Brenneman, UGA peanut research pathologist says they are looking at some shifts in sensitivity of white mold pathogen to some of the chemistries we use. “We have looked at several hundred isolates and we are seeing changes in sensitivity,” Brenneman says. “Looking at our database from 20 years ago, we’re seeing that those isolates are not as sensitive to some of our main fungicides like flutolonil and tebuconozole. “We want to see how that affects control in the field and response to some of the newer fungicides like Elatus or Excalia that are in the same class of chemistry,” he says. “Does less resistance to older chemistries translate into less control in some of the newer ones? That is what we are looking at.” PG
Battling Disease In 2022: • Anticipate problems based on history and weather conditions. • Use Peanut Rx to determine risk level of fields. • Have a contingency plan if a first fungicide choice is not available. • Make sure you have disease protection on the seed and in the furrow. • Add an in-furrow nematicide or plant a resistant variety. • Be as ‘on time’ as possible with leaf spot protection. • Do not rely too heavily on SDHI products. • Tank-mix sulfur to increase leaf spot control.
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APRIL 2022 • THE PEANUT GROWER /
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