Fungicides: Bandwagon or Best Management?

Use of fungicides is soaring this year after research shows possible yield boost even in the absence of disease. By Anna Ziegler, Prairie Farmer intern

Published on: Jul 18, 2007

Crop dusters over Illinois corn fields have been thicker than pigeons on a statue this month. On the heels of promising agronomic research and effective marketing from chemical companies, use of fungicides is soaring.

The excitement stems from publicity about fungicides boosting corn yield even in the absence of foliar diseases. One chemical in particular, Headline, a BASF product, has attracted significant attention.

Trials conducted by the University of Illinois over the past three years confirm Headline can have a yield boosting influence on corn. The fungicide provided an average 6.2 bushels per acre over non-treated acreage, according to Emerson Nafziger, University of Illinois Extension agronomist.

Researchers suspect the fungicide increases yield by reducing the plant's respiration rate, stretching its supply of sugar.

Fungicide applications at tasselling using the label rate of 6.1 ounces per acre increased yield in nine of 10 trials. While there is clear evidence for a consistent yield increase, economic returns must be considered.

"At the reported cost of $20 to $25 per acre for the fungicide applied by air, the average response of 6.2 bushels would barely cover costs at $4 per bushel of corn," Nafziger writes.

In some U of I trials, yield response reached a 12 bushel per acre advantage, enough to return a profit. "Unfortunately we don't know how to predict when such a response will happen," Nafziger writes.

A nagging question for agronomists is whether farmers are carefully weighing the risks and benefits or suffering from a keeping up with the Jones syndrome in applying fungicides this season.

Extension agronomists encourage farmers to apply fungicides only when warranted. All applications should be made at the label rate because sublethal dosage can increase the risk of resistant fungal diseases.

For the full article about fungicide trial results and Emerson Nafziger's commentary visit www.ipm.uiuc.edu/bulletin/article.php?id=793