Looking at fungicides, other approaches to disease management

Many fungicides are available to help farmers fight the diseases that attack their crops. Those products can be expensive, however, and they do not always have the desired effect.

To help farmers choose the right fungicides for their needs, LSU AgCenter plant pathologist Boyd Padgett is studying the effectiveness of a wide range of commercially available and experimental products.

He also is looking into other approaches to disease management.

Padgett is evaluating hybrids and varieties of corn, grain sorghum, wheat and oats for disease resistance — seeing which are susceptible to diseases that are common in Louisiana and which ones are resistant to those pathogens.

Planting disease-resistant hybrids and varieties can prevent farmers from having to treat their fields with fungicides, saving them money. It’s also important in situations where no ideal options are on the market, which is the case with grain sorghum, Padgett said.

Padgett’s trials — which are conducted at the Dean Lee, Central and H. Rouse Caffey Rice research stations as well as on private farms — provide data that he shares with other scientists in the AgCenter and at universities across the country. This collaboration is not limited to fellow plant pathologists. That is because many areas of expertise are needed to identify hybrids and varieties — or breed new ones — that offer disease resistance and other desirable traits, such as high yield potential, all in one package.

“There’s a lot of effort that goes into it, and there’s a lot of different people involved,” Padgett said. “There’s agronomists and plant pathologists and breeders. It’s a lot of fun. It’s a team effort for sure.”

In a separate project focusing on soybeans, Padgett is examining whether when a crop is planted affects susceptibility to diseases, especially Cercospora leaf blight. He has planted test plots with different varieties and maturity groups on early, normal and late dates. These fields won’t be sprayed with any fungicides.

“We’ll just observe and see what diseases occur,” Padgett said.

Although rain and other factors can cause planting delays, farmers try to avoid putting soybeans in the ground too late so the crop isn’t still trying to grow when summer heat sets in. Optimum planting dates in Louisiana vary by location but typically fall between mid-April and mid-May.

“Once you get into June, you start losing yield,” he said.

The related choice of maturity group also may have an impact on disease issues. Varieties in maturity groups that mature rapidly aren’t in the field as long, leaving less time for diseases to develop. There is more opportunity for diseases to attack varieties that take longer to mature, but they have other advantages that lead farmers to select them.

Some new fungicides are showing promise as effective treatments for Cercospora.

“Prior to that, we didn’t have much. Some of the fungicides we had used aren’t effective now because the Cercospora populations developed resistance,” Padgett said. “Even if the planting date has only a minor effect, I’ll take it. There’s no silver bullet right now. But if you take fungicides, resistance and planting date, and combine all three, that could be an improvement.”

This story is featured in the Louisiana Soybean and Grain Research and Promotion Board 2020 Report.

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LSU AgCenter plant pathologist Boyd Padgett examines soybeans. Photo by Olivia McClure
9/16/2020 5:18:13 PM
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