ARS | Publication request: Timing of occurrence of Claviceps purpruea ascospores in northeast Oregon

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 2, 2010
Publication Date: November 23, 2010
Citation: Alderman, S.C., Walenta, D.L., Hamm, P.B. 2010. Timing of occurrence of Claviceps purpruea ascospores in northeast Oregon. Plant Health Progress. doi:10.1094/PHP-2010-1123-01-RS.

Interpretive Summary: Ergot is an important disease of Kentucky bluegrass which seed yield loss can exceed 25%.To determine whether variation in yearly ergot severity is due to timing of occurrence of spores of the ergot fungus, spore traps were used to monitor spores of the ergot fungus at two sites in NE Oregon during 2008-2010. Results suggest that Kentucky bluegrass may be at greatest risk for infection in years when flowering is early than normal. Predicting years of low ergot severity could save up to three fungicide applications annually for ergot control.

Technical Abstract: Ergot, caused by Claviceps purpurea, is an important floral disease of grasses, characterized by sclerotium formation within grass flowers. To determine whether annual variation in ergot in Kentucky bluegrass is a result of ascospore density and/or timing of ascospore occurrence, Burkard 7 day volumetric spores traps were used to monitor ascospores of C. purpurea in each of two Kentucky bluegrass fields in the Grand Ronde Valley in northeastern OR during mid May to late June, 2008-2010. Ascospores were typically trapped between midnight and 6:00 a.m. In 2008 and 2010, most ascospores were released prior to flowering in Kentucky bluegrass, corresponding to no observed ergot in 2008 and a low level of ergot in 2010. In 2009, ascospore release and pollination coincided, but few airborne ascospores were present, resulting in a low level of ergot. In 2008-2010, fungicides for ergot control were unnecessary. In years when there are few ascospores during flowering in Kentucky bluegrass, a reduction of up to three fungicide applications may be possible.