Back when fungicides for use in corn and soybeans were just a gleam in the eye of a chemical company marketing manager, a 1990s discovery intrigued European scientists.
They noticed that cereals treated for disease with strobilurin fungicides were much greener than untreated cereals. Digging a bit deeper, the chemical company scientists discovered these disease-fighting compounds also sliced ethylene production.
“Ethylene reduction is part of the reason why plants stay greener longer,” says Fred Below, University of Illinois plant physiologist. Scientists discovered other physiological benefits that may ultimately boost yields.
In the mid-2000s, these qualities struck a perfect storm in the Midwest. Soybean producers feared soybean rust would ravage their fields. They examined fungicides that southern U.S. farmers had used to protect soybeans from fungal diseases like frogeye leaf spot. In corn, shifting agronomic practices (like corn-on-corn and less tillage) that harbored disease were more conducive to fungicide responses.
Meanwhile, skyrocketing commodity prices helped make fungicide applications economically feasible. A 7-bushel-per-acre yield spike can cover a $32- to $34-per-acre fungicide and application cost much better at $6-per-bushel corn prices than it can at $3-per-bushel prices.
Soon, strobilurin fungicides (including Headline, Quadris, and Evito) and strobilurin premixes (including Quilt Xcel, Stratego, Avaris, and Headline AMP) became mainstream agronomic tools. Strobilurin fungicides particularly shine in disease-ravaged corn. University of Kentucky (UK) research showed that a 9.6- to 12-bushel-per-acre yield spike in 2009 occurred in fields with over 5% disease severity.
A three-year University of Tennessee and Pioneer Hi-Bred study showed disease-susceptible hybrids especially benefit from fungicide applications. Average yield gains of 23.5 bushels per acre resulted on disease-susceptible hybrids, compared to 7 bushels per acre for resistant ones. (See chart on page 36).
“There are some very good reasons for using them,” says Paul Vincelli, UK Extension plant pathologist. “I see it over and over again where fungicides show a favorable return where there is significant disease pressure.”
The water gets muddier when strobilurin manufacturers recommend strobilurin fungicide application with no disease present to garner plant physiology benefits.
BASF promoted the physiological impact of its Headline fungicides by trademarking the term Plant Health. In 2009, BASF took Headline's plant physiology benefits a step further when it obtained a federal supplemental label for its Headline products. Besides controlling disease, the supplemental label lists that Headline's benefits include improved plant tolerance to maladies like hail, drought, cold temperatures, ozone damage, and frost. The label also stated that Headline could improve plant use of nitrogen and increase tolerance to bacterial and viral infections.