Possible Microbial Influences on the Appearance of Rice Panicle After Laura

by By Yeshi Wameshi, Extension Rice Plant Pathologist - September 4, 2020

Harvest has been delayed in several rice fields in Arkansas due to a wet condition from the tropical storm, Laura. When harvest is delayed due to rain, one of the common phenomenon often seen is sooty mold.  Fields that received higher rates of nitrogen fertilization often show noticeable sooty mold. Discoloration from sooty molds can be worse in lodged rice. Sooty mold is caused by several opportunistic fungi that are collectively referred to as “sooty molds”.  Sooty mold in rice is blackening on kernel surfaces.  The molds are superficial (Fig. 1) and basically do not affect milled rice (Fig. 2). As far as we know, sooty mold does not directly reduce the quality of brown or milled rice. However, the appearance of the rough rice can be affected enough to be confused with kernel smut not only on farm but at the mill too.

Please note: if sooty mold appears repeatedly in your fields, it is highly possible that the level of nitrogen fertilizer is excessive. Application of proper levels on nitrogen and potassium fertilizers is necessary to harvest clean kernels. Generally, sooty mold can be reduced if your disease management strategy aims at an optimum yield while keeping disease pressure to the minimum.

Panicles affected by the wind from the storm may also be blank depending on the stage of the crop with ultimate dark discoloration due to saprophytic microbial growth (Fig .3).

Fig. 1. Rough rice superficially covered by sooty molds

Fig. 2. Sooty molds on rough rice may affect bran quality
but not the quality of brown or milled rice.

Fig. 3.  Wind damaged panicle (photo courtesy: Andrew Sayger, Monroe County August 2020)