Downy brome and Medusahead Control in Rangelands (1) with Rimsulfuron Ronnie G. Turner*, Jerry R. Pitts, Mike T. Edwards, Norman D. McKinley, C. William Kral, Craig M. Alford, John D. Cantlon DuPont Crop Protection 8295 Tournament Drive, Suite 300 Memphis, TN (1) Rimsulfuron is not currently registered in Rangelands

Downy Brome Bromus tectorum Photos: Steve Dewey, Utah State University; Chris Evans, University of Georgia

Downy Brome aka: cheatgrass Invasive grass - Native of southern Europe –Now Infests ~ 100 Million Acres in US –Quick Invader of heavily grazed rangeland, burned areas, and other disturbed sites Winter Annual –Dev large root system fall to spring; robs moisture –Deters native grass seedlings; reduces population –Dries down quickly by early summer; extended wildfire hazard –Early/often wildfires prevent native grass/sage regeneration which can decrease wildlife habitat Little Grazing Value –Bad taste; pulls up easily –Sharp seed pods injure mouths of grazing animals

MEDUSAHEAD Taeniatherum caput-medusae Photos: Steve Dewey, Utah State University – Bugwood web site

MEDUSAHEAD Invasive grass – Native of Eurasia –Infests large areas of PNW, CA –Usually more prevalent on Clay soils, but has also been found on sandy soils Winter Annual –Repro by seed; matures 2-4 wks later vs. other annual grasses –Fibrous root system – develops faster than downy brome –Depletes upper soil moisture early season (reduces germination potential for native grass seed) –Dead stems decompose slowly forming dense mats; increased fire potential Little Grazing Value –High silica content (unpalatable); stiff awns, hard florets can injure eyes, mouth of cattle

Rimsulfuron DuPont Sufonylurea Herbicide –Inhibits acetolactate synthase (ALS) Registered for Use in Field Corn, Potatoes, Tomatoes; registration pending in Fruit, Nut, Vine crops, and future uses expected in Roadsides and Rangelands Pre and Post activity on Grasses and Broadleaf Weeds –Root and Foliar uptake; moves in xylem and phloem Behavior in Water and Soil –At 25°C, half-life in water at 4.6 (pH 5) to 0.3 (pH 9) days –Across 4 soil types, half-life ranged 1.7 to 4.3 days at 86°F (30°C) –In Aqueous Solutions, half-life at 68°F (20°C) and pH 7 = 24 days at 50°F(10°C), pH 7 half-life at 144 days

Rimsulfuron – Downy Brome Application Timing: late Oct – early Dec

Rimsulfuron + Telar® Application Timing: late Oct – early Dec

Rimsulfuron – Medusahead Application Timing: late Oct – early Dec No. Tests ( )

Rimsulfuron + Telar® Application Timing: late Oct – early Dec

Downy Brome Rangeland Trial Location: Pleasanton, NE Application Date: 20-Nov-2005 Application Equipment: CO 2 Sprayer Application Volume: 14 gal/ac Weed Stage: Downy Brome, 2 to 4 tillers Crop Stage: Western Wheatgrass 2 to 4” Evaluation: 230 DAT (days after treatment)

Downy Brome ( 230 DAT ) Rim 0.75 oz ai/A +Surf UTC

Downy Brome ( 230 DAT ) Rim 1 oz ai/A + Surf UTC

Downy Brome ( 230 DAT ) Landmark oz ai/A + Surf UTC

Downy Brome ( 230 DAT ) Plateau 1.88 oz ai/A + Surf UTC

Medusahead Rangeland Trial Location: Boise, ID Application Date: 13-Oct-2005 Application Equipment: CO 2 Sprayer Application Volume: 20 gal/acre Plot Size: 10’ X 30’ X 3 Reps Pest Stage at Application: –Senescent Medusahead; Early Germination

Medusahead (195 DAT ) Rimsulfuron 1 oz ai/A + Surf UTC

Medusahead (195 DAT ) Rim 1 + Telar.375 oz ai/A + Surf UTC

Medusahead (195 DAT ) Landmark oz ai/A + Surf UTC

Medusahead (195 DAT ) Plateau 1.88 oz ai/A + Surf UTC

Rimsulfuron – Summary In these trials, Rimsulfuron provided excellent control of Downy brome Rimsulfuron provided good control of Medusahead rye (fewer tests) Install further tests in Fall 2006 especially for Medusahead Install Plant Back trials to evaluate Native Grass tolerance following Rim applications –Field Trails and University Field Station - NCal

THANK YOU !! QUESTIONS ???

Additional Slides - References

Cheatgrass / Medusahead References (web sites) Cheatgrass – – – –A homeowners guide to cheatgrass. Jay davison, Ed Smith, Cooperative Extension, University of Nevada, Reno – s.htmwww.explorebiodiversity.com/problem_plants/species/Cheatgras s.htm –

Cheatgrass / Medusahead References (web sites) Medusahead – erum-caput-medusae.htmwww.cdfa.ca.gov/phpps/ipc/weedinfo/taeniath erum-caput-medusae.htm – uality/MEDUSA.HTMhttp://californiarangeland.ucdavis.edu/water_q uality/MEDUSA.HTM – – shtmlwww.oregon.gov/ODA/PLANT/WEEDS/profile_medusaheadrye. shtml –