By Yeshi Wamishe, Extension Rice Pathologist, and Jarrod Hardke, Extension Rice Agronomist
Most rice in Arkansas is near or well past internode elongation (joint movement). Except for a few cases of seedling disease complexes and hydrogen sulfide toxicity, until now, blast and sheath blight rice diseases have been relatively quiet in Arkansas. Today (June 20, 2016), we received a report of leaf blast on medium grain rice variety Jupiter which is at ½” internode elongation in Woodruff County (Fig. 1). Last year blast in Arkansas appeared a week earlier than this year, and Jupiter was one of the widely affected variety.
Although the blast fungus has different mechanisms of survival and spread, early blast disease in susceptible varieties can be well suppressed with deep flood management. Often when the first emerged leaves dry and die back, blast tends to “disappear” and may not be a problem later in the season. However, if it prevails, blast can cause dramatic yield loss on susceptible rice under favorable conditions. The blast fungus infects collars, nodes, and panicles of the rice plant. Severe damage occurs when the fungus attacks the nodes. However, leaf blast can also do considerable damage to leaves (Fig. 2) and provide inoculum for neck blast later in the season. In general, it is difficult to predict the occurrence of the disease; therefore, scouting is highly recommended.
A tip on scouting blast disease on blast susceptible rice cultivars
Identify the possible parts of the fields where symptoms may start. Field areas such as water- limited field edges, levees, shaded field spots due to east or west tree lines, and denser field spots due to overlapped seeding and/or nitrogen fertilizer rates are potential areas for blast development. Sandier soils that do not maintain permanent flood or fields with limited water supply in general are also prone to blast. In such fields, blast disease can start anywhere in the field. If blast is found in the field, it is wise to flag that area so that it can be checked repeatedly to evaluate progress and spread of the disease. To read supporting research on the use of deep flood to fighting rice blast disease read: http://www1.udel.edu/udaily/2016/dec/rice-fungus-122215.html.