Research into rice disease control practices is a “core project” for the Louisiana Rice Research Board, said Felipe Dalla Lana, the LSU AgCenter rice pathologist who leads the team developing management strategies for the state’s most significant diseases.

This important project comprises a wide variety of studies that seek to assemble large amounts of data and make foundational recommendations to help producers.

“That’s why we are working on building these databases, building all this information,” he said. “The goal is to eventually have all these tools and a single environment or hub where the growers or stakeholders can go and get that information.”

Research into disease control has three guiding principles or pillars, Dalla Lana said.

“The first one is we want to develop solutions that are profitable for the growers,” he said. “With all these solutions, we are thinking more on what the growers can do to make more profit.”

The other two principles focus on maintaining the quality consumers expect from Louisiana rice and causing minimal environmental effects.

“We didn’t say we need to control all disease,” Dalla Lana said. “You can have a level of disease where it doesn’t reach an economic threshold where it costs much more for control.”

On the project, Dalla Lana works with AgCenter rice breeders, geneticists and plant pathologists, and the team has developed a relationship with Camila Nicolli, a plant pathologist at the University of Arkansas System Division of Agriculture.

In recent years, the rice disease control practices program has focused on sheath blight, blast, Cercospora, bacterial panicle blight and grain smuts as the most important diseases for Louisiana rice producers. These cause thin stands, lodging, spotted kernels, fewer and smaller grains, reduced milling, higher chalk and a reduction in plant efficiency, Dalla Lana said. The best defense against these diseases is a sound integrated pest management strategy, he said.

“Some of them we need to have a few years before we have results that we can trust,” he said.

This past year the ongoing project focused on studies into sheath blight and Cercospora along with assessments of fungicide resistance and observing commercially available varieties for their reactions to common diseases.

In 2024, the integrated disease management strategy project maintained over 70 trials. The team analyzed sheath blight by inoculating plants with the fungal disease and carried out four separate studies:

• Compared the fungicide efficacy of seven active ingredients labeled for rice
• Applied fungicides to three varieties that represented different levels of resistance to attempt to expand the application decision criteria for producers
• Tested different doses of azoxystrobin and flutolanil for sheath blight control
• Sprayed multiple doses of a fungicide at different stages to explore timing of applications

Another set of studies centered on Cercospora. Researchers explored two different timings of fungicide applications on eight varieties with differing levels of resistance to the fungal disease and also tested whether current application timing recommendations reflect the best advice for control of Cercospora symptoms on the sheath and panicle infections, now referred to as Cercospora net blotch and Cercospora panicle blight, respectively. The research team also tested prothioconazole, a fungicide recently labeled for rice that will likely become commercially available to Louisiana rice producers in the future.

Researchers analyzed commercially available varieties and new breeding lines for several diseases. Because the plots planted in April showed a high incidence of kernel smut, the team assessed additional plots for the pathogen. They also sampled 30 fields in Louisiana and some in Arkansas for fungicide resistance to sheath blight.

Additional studies are seeking to understand the association between the health of the main crop and the yield of the ratoon crop.

“If you protect the main crop, will it then reflect a better crop in the second crop, or are the two totally independent?” he said.

For 2025, the program will continue studies on fungicide efficacy, timing and integrated pest management, Dalla Lana said, with a focus on sheath blight, Cercospora and blast. The team will continue to analyze new breeding lines and commercial varieties for disease and support studies of new industry products for disease management.

These rice plants show symptoms of Cercospora, which is often known as narrow brown leaf spot. Photo provided by Felipe Dalla Lana