Occurrence of Viruses and Clavibacter michiganensis in Winter Wheat in Illinois, 2009 to 2011 and 2019 to 2020

Field surveys in 2009, 2010, 2011,2019, and 2020 determined the incidence and diversity of viruses present in fields of soft red winter wheat (Triticum aestivum) in Illinois. In addition, the putative presence of the bacterial mosaic pathogen, Clavibacter michiganensis subsp. tessellarius (Cmt), was evaluated. A total of 341 fields were sampled across years, and plants were tested for barley yellow dwarf virus (BYDV-PAV; BYDV-MAV), barley stripe mosaic virus (BSMV), brome mosaic virus (BMV), cereal yellow dwarf virus (CYDV-RPV), High Plains virus (HPV), Potyvirus group (POTY), soil-borne wheat mosaic virus (SBWMV), tobacco mosaic virus (TMV), wheat spindle streak mosaic virus (WSSMV), wheat streak mosaic virus (WSMV), and Cmt using ELISA. Average field incidence across years varied by virus with BYDV-PAV (22%), WSSMV (16%), CYDV-RPV (7%), WSMV (3%), and HPV (0.5%) detected in samples. The bacterial mosaic pathogen (Cmt), or potentially a related species of Clavibacter, was detected the most frequently in each year, with an average incidence of 77%. The consistent detection of Cmt warrants further study to determine the nature of the organisms associated with positive Cmt tests and their role in Illinois wheat production systems.