Management Strategies for Barley Yellow Dwarf on Winter Wheat in Kansas

Bockus, W. W., De Wolf, E. D., and Todd, T. C. 2016. Management strategies for barley yellow dwarf on winter wheat in Kansas. Plant Health Prog. 17:122-127. Barley yellow dwarf (BYD) is one of the most important wheat diseases in the state of Kansas. Several methods of disease management have been recommended to mitigate losses from BYD including the use of seedtreatment insecticides, delayed planting of winter wheat, and deploying cultivars with resistance to BYD. The goal of this research was to quantify the impact of these three management strategies, alone and in combination, on BYD disease progress and grain yields in Kansas. When field experiments were averaged over four years, treating seed with the insecticide imidacloprid (Gaucho) reduced the daily increase in the area under the disease progress curve (AUDPC) by 35.0% and corresponding yield losses from BYD by 16.4%. Compared with early planting, late planting reduced AUDPC by 47.9% and corresponding yield losses by 57.5%. Planting a moderately resistant cultivar reduced AUDPC by 80.9% and corresponding yield losses by 72.6% compared with a susceptible cultivar. When all three BYD management methods were combined, BYD was reduced by 95.2% and yield losses reduced by 97.1% when compared with not using any of the management methods. Therefore, integrating management practices can result in high levels of control of BYD in Kansas. SIGNIFICANCE OF BARLEY YELLOW DWARF IN KANSAS Barley yellow dwarf (BYD) is an important disease, occurs worldwide (Burnett 1984; Lister and Ranieri 1995; Plumb 1983), and is the fifth most important wheat disease in Kansas (Appel et al. 2015). That state is usually the nation’s number one producer of wheat and often plants about 4 million hectares. BYD is caused by several strains of viruses including Barley yellow dwarf virus (BYDV) and Cereal yellow dwarf virus (CYDV). The strain most often detected in wheat in Kansas is PAS (BYDV) although PAV (BYDV) and RPV (CYDV) can also occur in significant amounts in certain fields (Acosta-Leal et al. 2013). The most common vectors of these viruses are the bird cherry-oat aphid (Rhopalosiphum padi) or the greenbug (Schizaphis graminum) (Fig. 1) (Gildow 1987; Power and Gray 1995). The most typical symptom of BYD infection is discoloration of leaves with yellow discoloration the most common (Fig. 2); however, certain wheat genotypes also show orange, red, or purple leaf discoloration (Fig. 3). In Kansas, symptoms typically begin to appear in April as the wheat goes through the jointing growth stage. From that point, the percentage of plants displaying symptoms will usually increase until natural senescence begins. After heading, other symptoms can appear such as tiller stunting and darkening of the heads at maturity. The stunting symptom is usually associated with early infections of the wheat plant in the fall (Goulart et al. 1989). BYD can cause significant yield losses in wheat (Fig. 4). For example, yields were reduced by 46% in BYD-infected wheat and 58% when virus-infected wheat was simultaneously infested with R. padi (Riedell et al. 1961). There are several other reports documenting yield losses between 32 and 53% (Herbert et al. 1999, 34%; Hoffman and Kolb 1998, 36%; McKirdy and Jones 1996, 43%; McKirdy et al. 2002, 33 to 53%; Perry et al. 2000, 35%; and Weisz et al. 2005, 32%). Another report (Patterson et al. 1990) estimated regional losses due to BYD of 2 to 10%. Similar losses (22 to 49%) have been reported for BYD in winter wheat in Kansas (Bockus 1994; Bockus 1997; Bockus and De Wolf 2013; Bockus and De Wolf 2014; Bockus et al. 2015).