Fungicide a key tool for soybeans, regardless of planting date

Soybean diseases such as frogeye leafspot, Cercospora leaf blight and target spot are becoming bigger problems for Illinois farmers. (Photo by Catrina Rawson)

Soybean planting dates were all over the board as usual this season, with some farmers choosing to plant earlier while others are still finishing up.

But that shouldn’t affect plans for fungicide applications. Farmers should target the R2 to R4 soybean growth stage, with R3 still viewed as the optimum time to apply fungicide, according to BASF representatives from Illinois.

Mike Probst, BASF technical services representative, and Greg Ury, BASF agronomist, discussed the use of fungicide and its link to higher yield potential during a virtual meeting hosted by the Illinois Soybean Association.

“It’s been a pretty interesting spring,” Probst said. “We had some (soybeans) planted in early April, which faced quite a bit of cold temperatures but have finally taken off and are looking good. Some were planted in late May or early June. And some (farmers) are still planting, particularly double-crop beans.

“Even though there’s quite a bit of variability from field to field, our plans for fungicide use haven’t changed that much,” he noted.

The industry representatives report an uptick in fungicide use over the years, and for good reason. It not only controls diseases as its main objective, but it also can reduce the overall effect of environmental stress on crops, thus leading to higher yields and better returns.

“The use of fungicides in soybeans has really gained a lot of popularity,” Probst said. “It’s something that provides a lot of benefits.”

Diseases becoming more of an issue in soybeans include frogeye leafspot, mostly in central and southern Illinois, along with Cercospora leaf blight and target spot to the south, Probst said.

Crop disease outbreaks not only limit resources that could be used for growth and grain fill, but infections also can lead to plant tissue death, thus lowering photosynthetic capability, and stress the crop during important growth stages.

“A disease is kind of like weeds. It steals nutrients and resources,” Probst said. “All (the effects) have a negative yield impact.”

BASF conducted a trial of five different planting dates, ranging from April 7 to June 16, with four different soy varieties in Seymour and found the treated beans all had yield responses between 2.3 and 4.7 bushels per acre, even without significant disease pressure.

Moving south, a BASF three-year trial on soy response to foliar fungicide conducted at Southern Illinois University in Carbondale found an average yield gain of 8.2 bushels per acre, according to Probst.

And, fungicide response trials at six locations (Belleville, Bloomington, DeKalb, Macomb, Seymour and Springfield) last year found an average yield boost of 5.1 bushels per acre on the treated beans, Ury reported.

“We’re seeing fungicide responses despite the lack of disease,” said Ury, who noted fungicide helps reduce environmental stress. “In DeKalb there was an 8.4 yield advantage. I attribute the yield response to drought stress as it got fairly dry (there) late in the (2020) season.”