Hot, dry weather may cause disease outbreak in rice

Bruce Schultz  |  7/12/2012 12:39:15 AM

News Release Distributed 07/11/12

LAKE ARTHUR, La. – If hot, dry weather continues, rice farmers should expect an outbreak of bacterial panicle blight, according to Don Groth, LSU AgCenter plant pathologist.

Groth told farmers gathered at the Vermilion Rice and Soybean Field Tour on July 5 that fungicides are not effective against bacterial panicle blight because it is caused by bacteria.

Groth said he is testing the new fungicide Sercadis to determine when two applications of the chemical is necessary for treating sheath blight disease that has become resistant to other fungicides.

Sercadis is not effective against blast disease, however, and Groth said blast this year is the worst he’s ever seen.

At test plots planted by LSU AgCenter rice breeders at the Lounsberry Farm near here, the rice crop appears relatively healthy. At the station’s field day June 28, visitors were shown plots that were heavily infected with blast, although the severity differed among varieties.

“There’s a night and day difference between what we’re seeing here (Lounsberry Farm) and what we’re seeing at the Rice Research Station,” said Steve Linscombe, LSU AgCenter rice breeder. The Rice Station is in Acadia Parish, just north of Vermilion Parish.

Linscombe said CL151 and CL261 have been more blast susceptible than he expected, while the varieties CL111, Mermentau, Catahoula and Cheniere are showing resistance.

“But that resistance is not going to last forever,” Linscombe warned. He said different races of blast disease exist that will eventually overcome resistance.

In fact, this year’s heavy disease presence will allow for selection of rice lines with good disease resistance, he said. “It will allow us to eliminate a lot of material.”

Xueyan Sha, LSU AgCenter rice breeder, said he is continuing his work on a Clearfield Jazzman variety with improved yields and enhanced cooking aroma.

Mike Stout, LSU AgCenter entomologist, said this year’s rice water weevil pressure is about normal. Dermacor used in water-seeded rice is showing good effectiveness, he said.

Stout also said stink bug pressure appears light so far.

Dustin Harrell briefed farmers on the use of a nitrogen soil test for rice, which is being evaluated for the second year in a three-year field scale validation trial on multiple producer farms. Harrell said the nitrogen soil testing for rice generally recommends normal nitrogen rates 80 percent of the time.

However, 20 percent of the time the soil test will recommend lower nitrogen rates, and these fields are being validated in the trials. Harrell said that last year’s nitrogen soil test recommendations worked in all but one instance.

If the testing shows good results this year and in 2013, the nitrogen soil test will become a recommended practice by the LSU AgCenter.

Harrell also said the LSU AgCenter is improving its soil testing program and recommendation reports to make it more user-friendly for farmers.

Ron Levy, LSU AgCenter soybean specialist, said early-planted beans are faring better than beans planted later. And he said beans planted in no-till fields, with some ground cover, appear to be doing better than beans planted on bare ground that holds less moisture.

He said hot weather is actually killing some plants. Soil temperatures taken recently showed some soil had gotten to 115 degrees in bare ground, and 95 degrees on no-till fields.

Soybeans look better in north Louisiana and in the areas where sugarcane is grown, he said, while southwest Louisiana soybeans are struggling in many places because of a lack of rainfall.

Levy said prices have jumped recently, now close to $16 a bushel.

Clayton Hollier, LSU AgCenter plant pathologist, said soybeans appear healthy. “I’m not seeing a tremendous amount of disease yet.”

He said soybeans can be infected with aerial blight that is resistant to most fungicides except a new one recently released, Priaxor. He said the fungicide-resistant aerial blight is the same disease as the fungicide-resistant sheath blight that has affected rice crops in Acadia Parish.

Bruce Schultz

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