Fungicide Costs vs Yield Gains - What Farmers Must Know
Farmers considering fungicide use this season are being urged to carefully assess whether the practice will deliver a real financial benefit. University of Missouri Extension state plant pathologist Mandy Bish highlights that increased yield does not always translate into profitability.
“We have a habit of assuming ‘yield increase’ and ‘return on investment’ are interchangeable,” says Bish. “That is not always the case.” She notes that in seasons with low disease pressure, the cost of fungicide application may outweigh any gains in yield.
With Missouri cash bids for No. 2 yellow corn hovering around $4 per bushel as of early March 2026, input decisions require extra scrutiny. Timing is a critical factor in determining whether fungicide applications are worthwhile.
Corn producers must also navigate the challenge of managing both tar spot and southern rust. Tar spot has appeared as early as June in Missouri, but Bish advises against premature spraying. The disease favors moderate temperatures between 64–73°F and often slows during the hotter conditions of mid-summer.
In contrast, those warmer and humid conditions can promote southern rust development. “If we spray too early for tar spot, we risk having no residual protection if southern rust moves into the area,” says Bish.
Research suggests the most reliable return comes from a single fungicide application between the VT/R1 and R3 growth stages. Growers generally need to protect at least 7.5 bushels per acre to break even, while two applications raise that threshold to about 15 bushels.
Soybean results are less predictable. “Across 66 on-farm strip trials, the average yield increase following a fungicide application was 1.8 bushels per acre,” Bish notes “Realistically, with current prices, a grower needs to see more than 3 bushels per acre to approach a positive ROI.”
Bish encourages growers to evaluate outcomes on their own operations. “I want farmers to confirm they are seeing the yield bump they believe they are getting,” Bish says. “Remember to factor in labor. Even if you aren’t paying someone else to spray, your time has a clear cost.”
FAQs
- Why should growers evaluate ROI before spraying?
To ensure fungicide costs are justified by actual profit gains.
- When is the ideal timing for corn fungicide application?
Between VT/R1 and R3 growth stages for best returns.
- Why is early spraying risky?
It may leave crops unprotected if southern rust develops later.
- How much yield gain is needed to break even?
At least 7.5 bushels per acre for a single application.
Photo Credit: gettyimages-luc-pouliot