Many people believe the future of corn production involves higher plant populations. But currently, populations as high as 40,000 plants per acre exert more stress on some hybrids than they can handle. Would it make sense to put limited fungicide dollars on fields where you’re pushing population?

“That was our theory,” says Trevor Perkins, an agronomist with Stewart Seeds. He helps conduct research as part of the Agronomy in Motion program. Perkins covers parts of Indiana, Ohio and Kentucky.

“It would seem to make sense that if fungicides help control diseases, that would alleviate stress, and stress is more of an issue with higher plant populations,” he says. “So perhaps more yield response would show when fungicides are applied to the same hybrid at a higher vs. normal population.”

First-year test
Perkins and other members of the Agronomy in Motion team set up an experiment to test the theory in 2016. They selected two sites: one in Jennings County, Ind., and one in Wood County, Ohio. They planted hybrids at two populations at each site. Targets were 32,000 and 40,000 plants per acre. The test was replicated three times at each location.

When they averaged data together from both sites, what did they find? “We saw a significant response to applying fungicide at both populations last year,” Perkins observes. In fact, the average yield difference was in the 25-to-30-bushel-per-acre range.

“What we didn’t see was a statistically greater yield increase at the higher population,” he adds. “We were hoping there would be more yield response where fungicide was applied at 40,000 compared to 32,000.”

Perkins also notes that to be more meaningful, tests need to be repeated in multiple years at multiple sites.

Disease whammy
Southern rust at the Indiana site was so devastating that it likely overshadowed any possible effect the agronomists were looking for, Perkins notes. “The response to fungicide at both populations was so dramatic because corn without fungicide succumbed rapidly to southern rust late in the season,” he adds. “It just pretty well masked any other effect that we might have seen in a year with more normal disease pressure.”

The Ohio site wasn’t impacted by southern rust because it was much drier there in 2016. In fact, water was at a premium during key stages of the growing season.

“We saw a small numerical advantage for fungicide at 40,000 vs. at 32,000 there, but it wasn’t significant,” Perkins says. “It was enough to make us think that there still might be value to our theory, but it certainly wasn’t enough to make any real claims. We’re a long way from saying that if you run into stress, like in a drought year, fungicide will help alleviate stress at higher populations and still allow you to harvest good yields.”

Stay tuned to see what the agronomists learn in 2017. Only one thing is certain — weather conditions won’t be the same as in 2016!