Conditions ripe for disease

The wet, humid weather of the past few days in Southwest Louisiana have enhanced conditions for disease on rice. (The rain gauge Friday morning showed .08 inches of rain in the past 24 hours, and rain is possible today. The previous day’s total was 1.9 inches.)
“This is going to bring it on,” said Dr. Don Groth, LSU AgCenter pathologist at the Rice Research Station. “This is perfect weather for disease.”
He said the blog field showed some potential signs of narrow brown spot caused by the cercospera disease. Up to five fields in the area are showing signs of Cercospora, but lab tests are needed to confirm its presence, he said.
The photo at right shows the narrow lesions that Groth, pictured above, suspects are caused by Cercospora.
This isn’t the only disease to worry about, however.
“Everything that keeps that canopy wet is perfect for sheath blight,” Groth said.
The window for spraying fungicides is quickly approaching. He recommends waiting until rice is between the mid-boot stage to 50-75 percent heading before making an application. Even though some signs of disease are showing up, he said, it’s best to wait for that time frame to get optimum effectiveness. For the blog field, Groth estimates the best time to spray will be in late June.
The blog field’s low seeding rate (42 pounds per acre) means the canopy isn’t thick yet, so that will slow down disease development, Groth said. But it will be treated with fungicides anyway because the field is being grown for seed rice.
He said Quadris is usually in the fungicide regimen, but this year Quilt or Stratego will be used because both chemicals contain propiconazole which is effective on Cercospora.
“The fungicides are already ordered and the plane will be here at the appropriate time,” he said.