“The application of foliar fungicides on soybeans has kind of followed the use of foliar fungicides on corn. When we saw the increase in corn acres being sprayed, we also saw an increase of a similar trend with soybeans,” said Carl Bradley, plant pathologist, University of Illinois.
The weather in 2014 for much of the Corn Belt was a year when foliar fungicide use was a little more likely to result in a positive yield response because of the potential for a yield increase in controlling a variety of diseases. It was a year of environmental conditions that were good for foliar diseases.
Bradley noted that a highly effective fungicide application should be one of a product with more than one class of chemistry.
“If you use a product that contains two active ingredients and one of them is known to be a little bit better curative and the other a little bit better preventive, that is fine, but I think maybe more importantly is that they have two different modes of action as well,” Bradley said.
With both soybeans and corn, there are risk factors other than the weather to consider in whether a fungicide application is likely to be appropriate for the most common economically impactful diseases.
A high risk factor for corn is planting hybrids that are susceptible to diseases like gray leaf spot and northern corn leaf blight. For portions of the soybean-producing area in the U.S., frogeye leaf spot is a common foliar disease that can economically impact yields, but there are others.
Planting corn on ground that was planted in corn the year before, or soybeans on ground planted to soybeans the year before, means disease pathogens could overwinter in the stubble and trash. Also, with acres that are conservation tilled, the crop trash will harbor those disease pathogens on the surface.
In some more northern areas, anthracnose leaf blight and stalk rot has been increasing.
“Anthracnose is becoming more of a problem because more farmers are using tillage tools that leave a lot of the corn trash on the surface,” Mark Varner, senior technical sales representative for eastern Michigan, said in repeating the major risk factor noted by Bradley.
Anthracnose leaf blight can show up early and then reappear later in the season, according to Bradley, with it being more of a northern tier disease.
Controlling the combination of corn diseases in Michigan with Stratego YLD applied at approximately the V5 stage has shown a positive yield impact in most instances, according to Varner. “We have done a lot of studies in side by side comparisons, and we’ve seen around a five to six bushel yield increase with an early-season Stratego YLD application compared to no fungicide application,” he said.
“Most of the time, the worse you are going to do is get your money back,” Varner added. Also, anything that can possibly increase corn standability and reduce lodging from stalk rots is highly appreciated by farmers, he said.
The V5 to V7 fungicide application is not the most common or even the highest return on investment potential because an application at R1 has traditionally shown control of foliar disease at the most critical time. In high pressure disease situations, an early and late application of Stratego, which is a combination of prothioconazole and trifloxystrobin has made economic sense, based on what Varner has seen.
As for northern soybean diseases, Varner says Septoria brown spot is common some wet years and can be controlled by Stratego YLD. White mold is similarly common and using Proline fungicide followed by Stratego YLD about 14 days later has been successful.