A decade ago, few farmers thought about using a foliar fungicide on soybeans. Then fungicide prices declined, crop prices had a nice run and yields continued to increase. Diseases and insects didn’t let up, so fungicide use intensified.
Since 2015, the Farm Journal Test Plots have studied fungicide use, initially as it relates to disease pressure. From there, Farm Journal Field Agronomists Missy Bauer and Ken Ferrie have more closely examined the plant health response and where the yield benefit actually comes from.
In 2019, foliar fungicide use in the Michigan test plots increased yield by 3.47 bu. to 4.7 bu. per acre versus the control. The average four plot locations in southern Michigan was 4.23 bu. per acre. Over the course of four years (2015 to 2019) that average increased to 4.91 bu. per acre (with a range of 5.9 bu. per acre in 2015 to 2019’s average).
Based on Farm Journal Test Plot research, the soybean yield increase from foliar fungicide use comes from the following:
- Keeping plants greener longer. “From our observations, using a foliar fungicide keeps the plants greener longer and extends the grain-fill period. In essence, it makes our shorter-season varieties act like a longer-season soybean,” Bauer explains.
- Increase in seed size. Bauer evaluated the main yield components (pods, seeds per pod and seed size) to determine where the yield response to foliar fungicide originates. There was little to no difference in pods and seeds per pod, however fungicide use did increase seed size.
Based on 2018 research, when a foliar fungicide was applied, soybeans averaged 2,816 seeds per pound versus the control at 2,957 seeds per pound, which means the seeds were smaller in size in the control. This increase in seed size alone is equivalent to an increase of 4.1 bu. per acre.
Knowing how foliar fungicide use impacts yield prompted additional questions about getting the most out of the fungicide dollar.
Does fungicide pay on late-planted soybeans?
In 2019, Bauer planted soybeans on April 25 and May 28 to compare how early- versus later-planted soybeans respond to a foliar fungicide application.
The soybeans with fungicide planted in late April yielded 4 bu. per acre more compared with the control with no fungicide (63 bu. versus 59 bu.). In the late-planted soybeans, the response increased to 4.7 bu. per acre compared with the control with no fungicide (57.9 bu. versus 53.3 bu.).
“Extending the grain fill period by keeping plants greener longer was even more important in the late-planted soybeans,” Bauer says.
Does timing matter?
The industry standard for fungicide application timing is typically the R3 growth stage, if no major disease pressure has been detected to that point. At the R3 stage, the plant is beginning to pod and one of the four uppermost nodes has a pod that’s 3/16" long. Knowing the primary yield response to fungicide use stems from an increase in seed size, Bauer wanted to evaluate if a later application would be more economical. In 2019, she compared the traditional R3 timing to R5 as well as a double pass (R3 and R5 applications). At R5, the seed is ⅛" long in the pod at one of the four uppermost nodes on the main stem.
“First-year results found a 1-bu.-per-acre gain with the R5 timing versus R3,” Bauer says. “There was no added benefit from a double pass.”
Does product type matter?
The Farm Journal Test Plots have been testing old versus new fungicide chemistry. The new chemistry contains new active ingredients or more modes of action. The 2019 test plots used: Revytek, a three-mode of action product from BASF; Trivapro, a three-mode of action product from Syngenta; and a new three-mode of action product coming in 2020 also from Bayer.
Bauer will continue to evaluate fungicide response to early- versus late-planted soybeans in 2020 as well as continue her timing and product type research.
We’ll share fungicide results from white mold plots and analysis from the Farm Journal Test Plots in Illinois as soon as harvest is over and the numbers are tallied.
Thank You to Our Test Plot Partners
Can-Am, Case IH, Clarks Ag Supply, Great Plains, Hagie, New Holland, Unverferth, AeroVironment, AirScout, BASF, Bayer, Syngenta, Finegan Farms, Bob Miner, North Concord Farms, Simington Farms, B&M Crop Consulting
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