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ARS Home » Pacific West Area » Logan, Utah » Forage and Range Research » Research » Publications at this Location » Publication #167822
Title: MEDUSAHEAD (TAENIATHERUM CAPUT-MEDUSAE) CONTROL WITH FALL-AND SPRING-APPLIED HERBICIDES ON NORTHERN UTAH FOOTHILLS

Author
item Monaco, Thomas
item OSMOND, TRAVIS - UTAH STATE UNIV.
item DEWEY, STEVEN - UTAH STATE UNIV.

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2004
Publication Date: 9/1/2005
Citation: Monaco, T.A., Osmond, T.M., Dewey, S.A. 2005. Medusahead (taeniatherum caput-medusae) control with fall-and spring-applied herbicides on northern utah foothills. Weed Technology.

Interpretive Summary: Medusahead (Taeniatherum caput-medusae) is an aggressive, non-native, winter annual grass that infests rangelands in the western United States. Its ability to rapidly spread, out-compete native vegetation, and destroy forage potential is a primary concern for landowners and land managers exposed to this weed. Prescribed burns were conducted at two study sites in northern Utah prior to conducting experiments to evaluate the effects of fall and spring applications of sulfometuron at 39 or 79 g/ha, imazapic at 70 or 140 g/ha, and a spring application of glyphosate + metsulfuron at 559 + 11 g/ha on medusahead and associated perennial grasses, annual and perennial forbs, and bare ground cover. Large differences in pre treatment medusahead litter between the sites resulted in less surface area burning at the low litter site (~10%) compared to the high litter site (~80%). Fall-applied herbicides were generally more effective in controlling medusahead than spring-applied herbicides. The high rate of fall applications provided significantly greater medusahead control than the low rate, but decreased cover of perennial grasses at the low litter site. In the second year, annual forb cover at the low litter site was significantly greater in the high rate than the low rate for sulfometuron and imazapic when applied in the fall, and for sulfometuron applied in the spring. Thus, annual forbs increased and perennial grass cover decreased as herbicide rate increased, suggesting that annual forbs were more released and better capable of capitalizing on available moisture and nutrients not used by medusahead. Our results collectively demonstrate that potential exists to successfully control medusahead and produce a window of opportunity to potentially reintroduce a greater abundance of perennial species back into the plant community.

Technical Abstract: Medusahead (Taeniatherum caput-medusae) is an aggressive, non-native, winter annual grass that infests rangelands in the western United States. Its ability to rapidly spread, out-compete native vegetation, and destroy forage potential is a primary concern for landowners and land managers exposed to this weed. Prescribed burns were conducted at two study sites in northern Utah prior to conducting experiments to evaluate the effects of fall and spring applications of sulfometuron at 39 or 79 g/ha, imazapic at 70 or 140 g/ha, and a spring application of glyphosate + metsulfuron at 559 + 11 g/ha on medusahead and associated perennial grasses, annual and perennial forbs, and bare ground cover. Large differences in pre treatment medusahead litter between the sites resulted in less surface area burning at the low litter site (~10%) compared to the high litter site (~80%). Fall-applied herbicides were generally more effective in controlling medusahead than spring-applied herbicides. The high rate of fall applications provided significantly greater medusahead control than the low rate, but decreased cover of perennial grasses at the low litter site. In the second year, annual forb cover at the low litter site was significantly greater in the high rate than the low rate for sulfometuron and imazapic when applied in the fall, and for sulfometuron applied in the spring. Thus, annual forbs increased and perennial grass cover decreased as herbicide rate increased, suggesting that annual forbs were more released and better capable of capitalizing on available moisture and nutrients not used by medusahead. Our results collectively demonstrate that potential exists to successfully control medusahead and produce a window of opportunity to potentially reintroduce a greater abundance of perennial species back into the plant community.