Maize Debris Increases Barley Yellow Dwarf Virus Severity in North Carolina Winter Wheat

In the eastern United States, wheat ( Triticum aestivum L.) is often planted with minimal or no tillage into maize (Zea mays L.) residues. We conducted a field experiment in the North Carolina Piedmont to compare the effects of three maize residue treatments (unchopped, chopped, and removed) on Fusarium head blight (FHB) in two winter wheat cultivars. While FHB levels were too low for meaningful comparisons, severe epidemics of barley/cereal yellow dwarf virus (YDV) did develop in 2 yr out of 3. In those 2 yr, YDV symptoms of discoloration and stunting were greater ( P ≤ 0.001), and yield was lower ( P ≤ 0.01), in plots with maize residue than in plots without maize residue. In the third year, when planting was late because of a severe fall drought, no YDV epidemic developed, and there were no differences in wheat yield due to maize residue treatment ( P = 0.25). In the first 2 yr, leaf samples from all plots were assayed for viruses using a multiplexed reverse transcription polymerase chain reaction (RT‐PCR) method. The most common YDV serotypes were MAV, PAV, and RPV, which were each detected in at least 46 and 74% of samples in the 2 yr, respectively. Our finding of greater YDV severity in association with surface residue is consistent with the reported aphid preference for high‐intensity yellow colors, which we hypothesize attracted aphids preferentially to residue‐covered plots in the fall. Our results support a recommendation of seed or seedling insecticide treatment when planting wheat into heavy unincorporated maize residue in the U.S. Piedmont.