Skipped Fungicide Cost Iowa Corn 50 Bushels as Drone Imagery Exposed Disease

Corn fields near Ames that yielded 252 to 260 bushels per acre last year under fungicide protection came in around 200 bushels this season after southern rust went untreated. That 50-bushel gap, reported by Dan Bjorklund, Technical Agronomy Lead at Landus Cooperative, anchors a fall agronomy picture in which drone imagery, nitrogen timing rules, and fertilizer purchasing decisions converge for Iowa retailers.

Bjorklund appeared on CropLife Retail Week alongside CropLife Editor Eric Sfiligoj and Amy Asmus, Co-Owner of Asmus Farm Supply, to discuss early harvest trends and fall decisions. Dryers near Asmus's northern Iowa territory have shut down for the season. Harvest is winding down there.

What did the drone imagery reveal?

Flying drones over customer fields, Bjorklund captured NDVI images — normalized difference vegetation index maps, where green signals healthy biomass and red signals trouble — unlike anything he had seen before. Small red spots polka-dotted the fields. Ground-truthing showed the plants in those patches were ghosted out by disease.

"It was like a warning sign to me, like the canary in the coal mine, that we've got some disease going on here, and this is going to have a yield impact," Bjorklund said.

One field near Ames, checked in late August, was riddled with southern rust. The grower had applied no fungicide at all. Sfiligoji noted other retailers reported growers skipping a second fungicide pass to save money, only to face heavy tar spot and gray leaf spot pressure.

Bjorklund said the zero-pass case was not typical. Most Iowa farmers applied at least one fungicide, though fewer passes than before. In the Boone area, growers who made two applications ran roughly 20 bushels ahead of single-pass neighbors. He cautioned the data is early and needs confirmation.

How is scouting technology carrying into next season?

Landus runs its SkyScout program on third-party software from a company active for the past three or four years. Every drone, plane, or satellite flight builds a timeline on the dashboard, letting agronomists pin anomalies during the season and revisit them with yield data in hand. Crown rot, which spread into parts of Iowa this year, becomes easier to trace in hindsight.

The software includes an AI agent that analyzes all enrolled acres. Bjorklund can compare hybrid genetics by brand, or pit fall-applied nitrogen plus spring product against fall-only programs. From now until farmer meetings begin in December, he will mine the season's data for correlations.

One grower between Britt and Forest City enrolled all his acres and, after disappointing results, now calls Bjorklund daily. The plan: review what the data shows, then discuss options for a difficult spring planting window, including genetics selection and newer systemic products that move through the xylem and phloem rather than working only on leaves.

Does the 50-degree rule still hold for anhydrous?

Yes. Asmus, citing Iowa State University maps showing 4-inch soil temperatures around 55 degrees in her area, reaffirmed that fall anhydrous and manure application waits for soils at or below 50 degrees. Stabilizers do not change that rule; at warmer temperatures they break down and denitrification claims the nitrogen.

Water quality scrutiny sharpens the stakes. Asmus said Iowa Extension offices already field calls from citizens watching fall nutrient applications amid constant media coverage of water quality.

Bjorklund, drawing on more than 30 years with Land O'Lakes and WinField United Answer Plots, said the economic optimum nitrogen rate has ranged from 120 to 240 pounds per acre depending on mineralization. His recommendation is firm: do not apply anhydrous above 50 degrees.

What does 2027 look like?

Growers who skimped on phosphate when prices ran high are back to at least replacement rates of phosphorus and potassium this fall, despite prices not falling. Soybean yields were phenomenal across northern Iowa, Bjorklund said, surprising nearly every farmer. Growers near Elkhart and Ames, where 10 inches of rain fell, face yields 50 to 60 bushels below neighbors and fewer options.

His priorities for December meetings: hybrid selection, biotic and abiotic stress products, and a hard look at nitrogen rates and timing. A price rally after the first of the year, depending on El Niño, could still shift grower plans.