Tolerance of Three Wheatgrass Cultivars to Sulfosulfuron Herbicide

Abstract

Crested, tall, and pubescent wheatgrasses are cool-season, drought-resistant perennial forages that grow well in semiarid environments and could complement wheat pasture grazing systems of the Texas Rolling Plains.  However, wheatgrass stand establishment is difficult due to competing winter grasses.  This study evaluated wheatgrass cultivars for tolerance to a sulfonylurea herbicide that may control competing annual grass weeds in wheatgrass stand establishment.  Utilizing greenhouse facilities, three rates of sulfosulfuron were applied preemergence, 2 weeks after emergence (2 WAE) at the 2-leaf stage, or 4 WAE at the 3- to 4-leaf stage to individual plants of ‘CD II’ (crested), ‘Jose’ (tall), and ‘Manska’ (pubescent) wheatgrasses.  Sensitivity to sulfosulfuron was least for CD II and greatest for Manska.  Considering all treatments and timings, Manska and Jose had greater declines in above-ground and below-ground biomass and fewer surviving seedlings than CD II. Wheatgrass cultivars were most sensitive to sulfosulfuron when treated 2 WAE.  Plant survival increased when sulfosulfuron application was delayed to 4 WAE, except for Manska where nearly 100% of the plants died regardless of herbicide rate.  A rigorous selection program with CD II could possibly lead to the development of a non-genetically engineered, sulfosulfuron-tolerant crested wheatgrass.