Rice Blast Can Take A Big Bite Out Of Profits In 2008

PORTAGEVILLE, MO.
   The current hot, dry weather in southeast Missouri, northeast Arkansas, and west Tennessee will retard development of rice blast, but this weather pattern may change. Rice farmers in these areas should scout their rice fields or hire a professional to scout their fields for blast from boot stage until head emergence is complete. Farmers should take action to manage this disease if blast symptoms are present on leaves at boot to split boot stage.
   If blast symptoms are present at split boot stage and the weather is predicted to be cloudy with frequent rains and heavy dew for the next 10 days, rice may be treated with Gem or Stratego (Bayer Crop Science), and Quadris or Quilt (Syngenta Crop Protection) fungicides. These fungicides should be applied for blast management when panicles begin to emerge from the boot (when the heads of 50 percent of the main tillers have emerged ¼ inch from the boot) and again 10-14 days later when panicle emergence is 80-90 percent complete (the heads of 50 percent of the main tillers have all emerged but for ¼ inch). Farmers may also raise the flood level to a minimum of 4 inches deep because this has been shown to retard development of blast in University of Arkansas trials.
   Blast is caused by a fungus that may infect leaves, nodes and panicles. Leaf spots are typically diamond shaped with a brown to redbrown border and a gray-white center. They may be 0.5 inches long and 0.25 inches wide, but size will vary. Yield loss will be severe when the disease develops on the nodes just below the head. This phase of the disease is called neck blast or rotten neck. The infected nodes will be discolored, the heads on these plants will turn white, and grain will not develop or develop poorly.
   University Extension Regional Agronomists can supply more information about blast, or you can call me at the Delta Center. More information about rice blast is also available at the University of Missouri-Delta Center Web Page, aes.missouri.edu/delta.
   Following these suggested procedures will give rice farmers a better chance to produce high yields and profits during 2008. Δ
   Dr. Allen Wrather is Professor Plant Pathology with the University of Missouri-Delta Center at Portageville.