Take Action Now to Resist Fungicide Resistance
While most row crop farmers aren’t experiencing this yet, it’s coming soon to their neighborhood.
While growers of specialty fruit and vegetable crops have seen plenty of problem diseases develop resistance to fungicides, it’s a relatively new concern for corn and soybean farmers. But like resistance to herbicides, the problem starts small in just a few counties or a state, and the resistant pathogens spread. Like herbicide resistance, the cause is overuse of fungicides with the same mode of action.
When the Take Action Program, a partnership of several universities and the United Soybean Board, expanded to include fungicide resistance and insecticide resistance, the goal was to bring awareness to the problem before it became as widespread as herbicide resistance.
Providing growers with the tools they need to make informed decisions about whether a fungicide is an economical option in a given circumstance is one way to reduce overuse. Education on alternative solutions for managing disease is another. Careful use of fungicides is the only way to preserve their efficacy for the future.
Carl Bradley, Extension Professor with the Department of Plant Pathology at the University of Kentucky, has been researching fungicide resistance on soybean pathogens since 2010. He and his team were the first to document a strobilurin-resistant strain of the frogeye leaf spot pathogen in fields in western Kentucky and western Tennessee. He recently published a paper documenting where they have found strobilurin-resistant diseases.
“It’s now in 14 different states,” Bradley says. “It’s become a pretty widespread problem, primarily where the North meets the South: southern Illinois, western Kentucky and western Tennessee, east Arkansas and southeast Missouri. It makes sense it’s where farmers consistently try to manage frogeye leaf spot. But there are other areas as well. At the University of Iowa, they’ve found they aren’t able to get control of frog eye leaf spot in certain places, and some isolates have been found with fungicide resistance.”
So far, frog eye leaf spot is the main problem, but Bradley said some strobilurin resistance has been seen in Septoria brown spot in Illinois and Kentucky, and in sheath blight in rice. Some resistance has been seen in some of the foliar
diseases in wheat, as well.
Rotate Crops, Rotate Control Methods
Bradley says it’s vitally important to not rely solely on fungicides for disease management. Not every field, or even every season, will require a fungicide application, he says.
“Assessing your risk is important,” he says. “On the Take Action website, we have a tool for scoring your disease risk in soybeans. You get points for different factors. If you’re above a certain score, it’s likely you will need a fungicide. If not, the disease risk is low, and applying a fungicide isn’t going to make much difference.”
Other disease management methods can also be quite effective, Bradley says. Choosing resistant varieties and rotating crops can go a long way.
“Many growers think they have to choose between resistant cultivars and high yields,” Bradley says. “The two are not mutually exclusive. There are some varieties that have a high yield potential and a good disease trait package as well. Do your homework and pick the right variety for the right field. Sometimes, that’s enough — you don’t even need a fungicide.”
Bradley says eliminating fungicides is not his goal, and he understands farmers need to be profitable.
“I’m an advocate for fungicides; they’re an effective tool when we really need them,” he says. “But they are really for disease management, and sometimes I think that message gets lost in the improved yield response messages that are used. But we don’t want to run into a problem — like we did with glyphosate in weed control— where fungicides are no longer effective. That will happen if we automatically spray everything all the time. We need to save fungicides for when we really need disease management.”
Be Part of the Solution
Many resources are available on the Take Action website, including a fungicide efficacy fact sheet and the Fungicide Lookup Tool. Visit www.IWillTakeAction.com/diseases