Residue Impacts on Stagonospora Glume Blotch in Wheat

Nathan Kleczewski, Extension Specialist – Plant Pathology;

Wheat season is well behind us and another season is fast approaching. One issue some growers encountered this season was Stagonospora leaf and glume blotch, a common disease of Delaware and Maryland wheat fields. There appears to be a trend of increasing incidence and severity of Stagonospora and other members of the leaf blotch complex (tan spot, Septoria blotch) in many regions where wheat is grown. This is likely a result of increased no-till or minimal-till acres. The use of no-till results in more wheat residue, which is used by the leaf blotch pathogens as an overwintering nutrient source. As a result, there is a greater potential for leaf blotch diseases due to the larger amount of local and regional inoculum.

Although it is likely that residue levels are related to leaf blotch outbreaks, little information exists on the impacts of residue on disease severity and yield. In a recent publication in the journal Phytopathology, a group of researchers set out to better understand the role of residue on winter wheat disease severity. Experiments were conducted from 2012-2014 using the wheat varieties Dynagro Shirley and Dynagro 9012. Four to six levels of residue were added to experimental plots. Disease severity was measured over time and yield calculated. What did the researchers find?

Glume blotch severity was associated with increasing residue levels. This was not a big surprise. However, the studies indicated that disease severity increased in a non-linear fashion. In fact, disease increased rapidly with relatively small increases of residue when residue levels were low, but leveled out somewhat when residue levels increased above 20-30% surface coverage. Disease severity ranged from 0-50% but only impacted yield at two sites. These results indicate that reducing residue can significantly reduce the impacts of Stagonospora glume blotch, but in order to see real benefits residue needs to be reduced below 30% coverage of the soil surface.

Mehra, L.K, C. Cowger, R. Weisz, and P. Ojambo, 2015. Quantifying the effects of wheat residue on severity of Stagonospora nodorum blotch and yield in winter wheat. Phytopathology: