ST. LOUIS, Mo. – Growers facing the threat of tar spot in corn and white mold in soybeans can now use Delaro fungicide to manage those diseases, thanks to a recent label amendment. The U.S. Environmental Protection Agency (EPA) approved the revision of the federal registration, adding tar spot and white mold to the long list of diseases that Delaro helps farmers manage.

“The label expansion reassures our grower and retail customers that we do have activity on these diseases,” said Dustin Schirm, Bayer customer business advisor for northern Iowa.

Delaro Controls Tar Spot in Corn

Tar spot is an aggressive pathogen that affects corn most often during the mid-reproductive cycle, appearing as black specks, almost like splattered tar on corn leaves. The disease eats away at healthy green leaf tissue and leads to increased lodging in corn. In 2018, yield losses were reported up to 30-40 bu/A, according to Michigan State University.

For some growers, 2019 was their first encounter with tar spot in their corn fields.

“It’s something we haven’t seen extensively until this year,” said Schirm. “It kind of crept in last summer and has expanded extensively around the state of Iowa.”

However, the Iowa growers who sprayed Delaro fungicide were able to better control the disease.

“Delaro performed exceptionally well this year on tar spot in Iowa,” said Schirm. “By spraying Delaro at the R1 or R2 stage we fought off tar spot moving in for at least three to four weeks.”

In an Iowa field trial, the untreated check was affected by tar spot very early, but the corn treated with Delaro showed no symptomology until the fungicide wore off. “In the treated corn, we had about a 23 bu/A response spraying Delaro,” Schirm added. 

Delaro Suppresses White Mold in Soybeans

White mold, on the other hand, causes yield loss in soybeans by reducing seed number and weight. The fungus eats away at the stems of healthy soybean plants, leading to decreased photosynthetic activity and premature death. This disease can cause yield losses of up to 50 percent, according to the University of Wisconsin – Madison. 

“If soybeans do get white mold, it can take a really good, healthy crop down to almost nothing,” said David Reif, a sales representative for Bayer in Michigan. “In my area, specifically, it’s a serious disease growers are thinking about every single year.” 

Fortunately, Delaro fungicide works to suppress white mold in soybeans.

“Delaro, with the two modes of action, and the prothioconazole in particular, does a really great job at helping with white mold suppression,” said Reif. “It protects the senescing flower petals, the primary infection point, and just does a really good job at preventing infection, or drastically reducing it, when the product is applied at the right timing.”

Reif recommends soybean growers apply Delaro between the R1 and R2 timeframe. When applied during this timeframe, some of Reif’s grower customers have seen anywhere from 10 to 15 bu/A yield increases, depending on severity of the white mold infection. 

“It’s definitely an exciting tool for soybean growers that deal with white mold on a yearly basis,” said Reif.

The amended label is an example of how Bayer is committed to supporting growers through innovative solutions. With the updated label, growers now have an additional way to help protect the health of corn and soybean crops from disease, while continually raising the bar on yields.

Delaro has two heavy-hitting modes of action to deliver excellent disease control. In addition to suppression of white mold, Delaro is labeled for other key diseases, such as frogeye leaf spot, aerial blight and brown spot in soybeans. In corn, Delaro also controls diseases, such as gray leaf spot, anthracnose leaf blight, common rust and southern rust, in addition to tar spot. With strobilurin and triazole components, Delaro provides long-lasting residual control for extended performance growers can count on through the season. 

In addition to disease control, Delaro improves plant health, promoting healthy, dark green leaves for improved photosynthesis. Delaro also increases plant stress resistance to support the full genetic potential of the seed. 

To learn more about Delaro fungicide and the diseases you can control using it, contact your local Bayer representative or visit