Corn Illustrated: Too Early To Tell if Fungicide Application Helped

Slight visual improvement in disease control noted in our test plots.

Published on: Sep 4, 2007

Was it worth spraying fungicide on corn in a dry year when little, if any, signs of disease were present? That answer won’t be known until the combine goes through the irrigated Corn Illustrated, high-yield plot this fall. The numbers of the yield monitor and yield map will tell the story.

The farmer cooperator, Jim Facemire, Edinburgh, Ind., walked portions of the field last week. Hearing horror stories of stymied ears that may or may not turn out linked to fungicide application, or to other materials applied with fungicides, he saw no signs of deformed ears, even in the 40,000 plants per acre test. Both 32,000 and 40,000 populations of two hybrids and 40,000 of a third hybrid were sprayed with Headline with a ground-driven rig after full tassel, while corn was pollinating. Check strips were left that were not sprayed for comparison purposes. It’s all part of the effort to try to reach 325 bushels per acre.

That goal is likely to remain elusive, even on irrigated soil this year. Whether it was too much heat, too much crowding, or the fact that irrigation doesn’t always mimic natural rainfall completely, one hybrid showed some tip dieback. It’s also possible that it’s just related to the genetics of that hybrid. The other two hybrids did not seem to be affected as much. Still, Facemire expects good yields on all three hybrids in the irrigated portion of the plot.

When Headline was applied on July 9, there was virtually no signs of leaf diseases on any of the hybrids, at any populations, Facemire notes. Soon after, however, humidity levels in central Indiana began increasing. They were much higher during the last half of July and well into August than during the summer to that point. Relatively high humidity levels are needed for certain diseases to grow and spread easily, including gray leaf spot.

Still, agronomists feel that ear development and even kernel fill were completed before enough disease moved in to likely affect yields. Besides, on non-irrigated land in drier areas of the Corn Belt this summer, crops began running out of water and died prematurely. It didn’t matter at that point if a lead fungal disease such as gray leaf spot was present or not.

When Facemire inspected fields last week, his visual gut check was that there was slightly less incidence of leaf disease on the rows treated with corn fungicide on July 9. However, it was only a visual observation. And even so, even if he noticed real differences, it’s difficult to tell if there was enough disease present to cause a yield drop of any kind, let alone an economic one.

So the combine will be the judge and jury this year. From the outset, it’s important to remember that not every year is like this one. Nevertheless, if there doesn’t turn out to be yield increases for applying fungicides this year in fields where there was no incidence of disease at the time of application, the ’07 could provide a valuable piece of information. It could help form the baseline for years when spraying won’t likely pay.