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ARS Home » Southeast Area » Raleigh, North Carolina » Plant Science Research » Research » Publications at this Location » Publication #310727
Title: Quantifying the effects of wheat residue on severity of Stagonospora nodorum blotch and yield in winter wheat

Author
item MEHRA, LUCKY - North Carolina State University
item Cowger, Christina
item WEISZ, RANDY - North Carolina State University
item OJIAMBO, PETER - North Carolina State University

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2015
Publication Date: 10/17/2015
Citation: Mehra, L., Cowger, C., Weisz, R., Ojiambo, P. 2015. Quantifying the effects of wheat residue on severity of Stagonospora nodorum blotch and yield in winter wheat. Phytopathology. 105:1417-1426.

Interpretive Summary: Stagonospora nodorum blotch (SNB) is a disease of wheat leaves, stems, and heads caused by the fungus Stagonospora nodorum. Wheat debris can be an important source of spores to start future epidemics, but the effect of different densities of infected debris on disease severity has not been previously determined. Experiments were conducted in two locations in North Carolina in each of three years, using the moderately susceptible winter wheat cultivar ‘DG-Shirley’. In the third year, the highly susceptible cultivar DG 9012 was added to the experiment and the study was conducted at one additional NC location. Debris was applied to plots so that different percentages of the ground were covered (0, 10, 20, 30, 60, and 90%). Disease was assessed several times in each plot, and disease levels, yield and test weight (grain density) were analyzed statistically. Yield and test weight were only significantly reduced by debris in one year, when disease was more severe. Overall, and of special importance for no-till producers, increasing amounts of wheat residue generally led to more intense SNB epidemics, but only had a significant effect on wheat yield in the most severe epidemic.

Technical Abstract: Stagonospora nodorum blotch (SNB), caused by the ascomycete fungus Stagonospora nodorum, is a major disease of wheat. Wheat residue can be an important source of inoculum, but the effect of different densities of infected debris on disease severity has not been previously determined. Experiments were conducted in Raleigh and Salisbury, North Carolina, in 2012, 2013, and 2014 using the moderately susceptible winter wheat cultivar ‘DG-Shirley’. In 2014, the highly susceptible cultivar DG 9012 was added to the experiment and the study was conducted at one additional location (Tyner, NC). Four (2012) or six (2013, 2014) treatments were applied in a randomized complete block design with five replicates. The treatments were 0, 10, 20, 30, 60, and 90% coverage of the ground with residue; 10 and 20% were added in 2013 and 2014. Whole-canopy disease severity (DS) was assessed three or four times in each plot. Area under the disease progress curve (AUDPC), maximum DS, yield, test weight, and thousand-kernel weight were subjected to analysis of variance. In both 2012 and 2013 at Raleigh, and in 2012 at Salisbury, disease measures at the 30 to 90% residue coverage (RC) levels were significantly higher than at the 0% RC level. In 2013 at Salisbury, AUDPC was higher at RC levels of 20% and above than in the control. In 2014 at all three locations, AUDPC for 0% RC was significantly less than for 10% RC or higher. Notably, the effect of RC on yield was significant in 2012, the higher-disease year, at both locations, but not at any location in the other two years. Test weight was only significantly affected in Raleigh in 2012, and thousand-kernel weight was not affected. Overall, and significantly for no-till producers, wheat residue generally resulted in greater SNB epidemic intensity, but only had a significant effect on wheat yield in the most severe epidemic.