DISEASES IN IRRIGATED BLUEGRASS SEED FIELDS AS AFFECTED BY POSTHARVEST RESIDUE REMOVAL METHODS

J. W. Sitton, W. J. Johnston and C. T. Golob

Department of Crop & Soil Sciences, Washington State University, Pullman, WA, USA

With increasing restrictions on open-field burning, Pacific Northwest, USA, seed growers are seeking alternative methods to remove postharvest residue from Kentucky bluegrass (Poa pratensis L.) seed production fields.  It is unclear how alternative, non-thermal systems will affect disease development in grass seed fields.  This study was conducted to determine which diseases were most prevalent in the absence of postharvest open-field burning and to evaluate alternative non-thermal residue removal management practices on disease severity.  Field experiments utilizing several postharvest removal techniques were conducted from 1993 to 1996 on irrigated bluegrass seed fields in northern Idaho to evaluate their effect on disease severity.  Ergot (Claviceps purpurea [Fr.] Tul.) and silvertop (Leptopterna dolabrata L.) were determined to be the most important diseases.  Fusarium poae was isolated from grass stems with silvertop symptoms; however, insects or mites were not detected on culms.  Compared to the current grower practice of baling, mechanical residue removal with a rotary rake, flail + needle nose rake, or crewcut-vacuum sweeper reduced the severity of ergot and silvertop.  Vigorous mechanical postharvest residue removal may mitigate disease development in irrigated bluegrass seed fields.

Keywords: ergot; Kentucky bluegrass; meadowgrass; silvertop.