Rice disease fairly stagnant in 2022 … until the late-summer rain fell

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LSU AgCenter rice pathologist Felipe Dalla Lana explores some of the latest lines to be grown in the greenhouses of the H. Rouse Caffey Rice Research Station. Dalla Lana brings a quantitative approach to the Rice Research Station’s Rice Pathology Project. Photo by Derek Albert/LSU AgCenter

For Louisiana rice producers, the 2022 growing season offered two narratives for disease in rice fields.

First, the warm and relatively dry spring and summer seasons saw little in the way of rice crop diseases. But when the near-daily late summer rains blanketed south Louisiana, disease pressures ramped up, especially in late-planted rice fields, according to Felipe Dalla Lana, plant pathologist at the H. Rouse Caffey Rice Research Station.

Dalla Lana cited what plant pathologists call the disease triangle to describe the pattern of disease that occurred in 2022. The disease triangle outlines that for disease to be present there must be three factors: the plant must be of a variety that is susceptible, a pathogen for the disease must be present and the environment must be conducive to the disease.

“What we had this year was the two first components, but for most of the time we didn’t have the environment that was conducive,” he said.

Even in instances where all three components of the disease triangle are present, there may not always be a need for mediation, he explained. The objective for the Rice Research Station’s pathology project is geared more towards helping growers produce a viable rice crop with a focus on economic stability.

“The goal of our program is not necessarily to have no disease in the fields, but to have control at an economical and environmental level,” Dalla Lana said. “This means that we don’t necessarily have to have disease-free fields, but our fields must produce as much as they can with a minimal level of fungicides or any other intervention that we have to do to control the disease.”

“Sheath blight continues to be the biggest concern, especially in the fields that are in a rice-soybean rotation,” he said.

Rice is a welcoming host for Rhizoctonia solani which causes sheath blight in rice and infects soybean fields as aerial blight. The inoculum that causes sheath blight overwinters in the soil until it has a healthy host plant to latch onto or until it eventually decays. In fields that have been in a rice-soybean rotation for recurring seasons, that inoculum has built up over time, providing better chances for the field to be infected. Therefore, in fields with historically high levels of sheath blight or soybean aerial blight, producers can expect a higher risk of developing a severe epidemic of sheath blight in the following year. Dalla Lana said for producers to stave off sheath blight, plant a non-host crop or put the affected field in crawfish rotation.

Although blast was not a major concern in rice fields in 2022, Dalla Lana said prevention is the best course. He said it starts with choosing varieties that contain the Pita gene. The Pita gene in rice prevents infection by Pyricularia oryzae, the fungus species that causes blast.

A proactive step in averting blast and other rice diseases is to avoid a high-nitrogen fertilization regimen, he recommended. “There are a lot of biochemical and physiological components to this, but to simplify, nitrogen facilitates the fungus infection and colonization of the plant,” he explained.

While fungicides can aid in controlling blast, sheath blight and other diseases in rice fields, Dalla Lana cautions that they are not a guarantee. Prevention remains a key to producing a viable rice crop.

“Do not rely only on the fungicide, but choose your variety, know your fields and plan your management based on this,” he said.

2022 marks Dalla Lana’s first year as pathologist at the Rice Research Station. Kurt Guidry, resident coordinator at the station, said Dalla Lana brings a quantitative research approach to plant pathology that he garnered from academia in his home country of Brazil and, more recently, The Ohio State University and Penn State University. Dalla Lana said his quantitative approach is dependent upon organizing research data compiled at the research station over many previous years. He said the data will be the building blocks to start this new quantitative research.

“There are a few components to this,” he said. “We have to look back at what was done in the past and use that information — the historical data — to see what happened in the past. We want to use the data for a different view to get new answers.”

Under Dalla Lana’s leadership, the rice pathology project will continue to test new fungicide products and will soon incorporate new faces at newly created positions to further explore rice diseases with a new research approach.

11/21/2022 5:46:13 PM
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