The Big Picture: Spraying Less, Saving More
Farmers often ask: “Does spraying fungicides at the R3 growth stage really pay off?”
To find out, University of Missouri Extension partnered with farmers across the state in an on-farm strip trial project. Over seven years and 64 fields, the results gave us a clear picture:
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Fungicides sometimes boost yields.
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But most of the time, the cost of spraying is higher than the extra beans you get back.
In other words, while fungicides can occasionally help, for the average Missouri farm, they’re usually not worth the investment.
Project Overview
A seven-year study led by University of Missouri Extension suggests that many Missouri soybean farmers may be losing money when applying fungicides at the R3 growth stage.
Since 2018, researchers have tracked on-farm strip trials across the state to evaluate the impact of fungicide use. The results? While fungicide applications sometimes boosted yields, the gains were usually too small to offset the costs.
On average, yields increased by just 1.8 bushels per acre after fungicide treatment. At a soybean price of $10.20 per bushel, that translates to roughly $18.36 in additional revenue. But with application costs running between $30 and $40 per acre, most farmers ended up losing about $15 per acre .
“Foliar disease pressure in Missouri is often low,” said lead researcher Mandy Bish, a plant pathologist with MU Extension. “That means applying fungicides for diseases isn’t typically justified — and in some cases, it even reduced yields.”
The data showed wide variability. In the best case, one field gained 12 bushels per acre. In the worst, yields dropped by nearly three bushels. Early models suggest weather may play a role, with rainfall within 48 hours of application potentially boosting effectiveness.
The project also revealed broader benefits. Fewer fungicide applications could slow the development of resistance, preserving tools for when farmers truly need them. “Decreasing unnecessary applications helps protect the effectiveness of these products long term,” Bish said.
For some farmers, the findings were eye-opening. One participant admitted he was skeptical at first: “I thought these results were crap when you first shared them at a field day. I own my sprayer, was leaving the field day to go spray my beans, was mad, and set up a strip trial myself. My results were almost identical to what you presented.”
For Missouri soybean growers, the bottom line is clear: fungicide applications at R3 may sometimes pay off, but more often they don’t. Researchers encourage farmers to think carefully about their fields’ conditions before reaching for the sprayer.
What We Learned
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Small Yield Bump: On average, applying fungicides at R3 added 1.8 bushels per acre.
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Costs Outweigh Benefits: With soybeans priced at $10.20/bushel, that’s about $18/acre in added revenue—while spraying costs $30–$40/acre. Farmers are often losing ~$15/acre.
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Wide Range of Results:
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Worst case: Yields dropped 3 bushels per acre.
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Best case: Yields rose 12 bushels per acre (only 1 out of 64 fields).
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Low Disease Pressure: Foliar diseases are often minor in Missouri, so spraying “just in case” doesn’t usually pay off.
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Weather Matters: Early models suggest that rain within 48 hours of spraying may improve odds of a yield boost.
Why It Matters for Missouri Farmers
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Save Money: Reducing unnecessary sprays keeps more dollars in your pocket.
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Fight Resistance: Using fungicides only when needed helps delay resistance and ensures products keep working when you really need them.
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Tailored Decisions: Farmers now have real-world, Missouri-specific data to make better management choices.
Real Farmer Impact
One Missouri farmer said after trying his own strip trial:
“I thought these results were crap when you first shared them… I set up my own trial and my results were almost identical. That opened my eyes.”
This kind of hands-on research shows how local testing + farmer involvement leads to better decisions in the field.
Next Steps
This study raises new questions:
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What happens when we add insecticides or biologicals to the spray mix?
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Which weather and soil factors increase the chances of a positive return?
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How do newer, more expensive fungicides compare to the older, cheaper ones?
These questions will guide future research, helping farmers refine fungicide decisions even more.