Chemical options for medusahead and barb goatgrass control Joe DiTomaso UC Davis Medusahead (Taeniatherum caput-medusae) Cal-IPC new list – High CDFA – List C Barb goatgrass (Aegilops triuncialis) Cal-IPC new list – High CDFA – List B Perseus used mechanical control effectively on medusahead. That is why he was considered a Olympian god. – Postemergence (at 2-8 leaf stage) • Glyphosate (Roundup®) applications control barb goatgrass and medusahead • Paraquat (Gramoxone®) older product, toxic • Clethodim (Envoy PlusTM) is effective where other desirable grasses are not present • Fluazifop (Fusilade®II) is also good but not registered in rangelands – Preemergence • Sulfometuron (Oust®) can also provide control • Combination of sulfometuron and chlorsulfuron (Landmark®) can damage some desirables in first year, but gives longer residual control • Imazapic (Plateau®) shows good potential for control of cheatgrass (not registered in California) • Rimsulfuron (Matrix®) shows good potential for control in first year • Auxinic herbicides, aminopyralid (Milestone®) and aminocyclopyrachlor (Method®) have activity at high concentrations – Postemergence (at 2-8 leaf stage) • Glyphosate (Roundup®) applications control barb goatgrass and medusahead • Paraquat (Gramoxone®) older product, toxic • Clethodim (Envoy PlusTM) is effective where other desirable grasses are not present • Fluazifop (Fusilade®II) is also good but not registered in rangelands – Preemergence • Sulfometuron (Oust®) can also provide control • Combination of sulfometuron and chlorsulfuron (Landmark®) can damage some desirables in first year, but gives longer residual control • Imazapic (Plateau®) shows good potential for control of cheatgrass (not registered in California) • Rimsulfuron (Matrix®) shows good potential for control in first year • Auxinic herbicides, aminopyralid (Milestone®) and aminocyclopyrachlor (Method®) have activity at high concentrations Medusahead control with low rates of glyphosate 35 30 Early season Mid season 25 Late season 20 Label states: “To control or suppress 15 medusahead, apply 11 oz/ac at 10 % medusaheadcover the 3-leaf stage” 5 0 0 2 4 6 8 10 12 14 16 18 Oz Roundup ProMax/acre Benefits: 1) lower cost, 2) safer on sagebrush, 3) reduced fire hazard Great Basin sagebrush steppe trial Untreated plot (left) vs. plot treated with a low rate of glyphosate at medusahead tillering stage (mid- season). Clethodim (0.5%), fluazifop (0.6%), and glyphosate (2%) control for barb goatgrass Change in occurrence frequency following 2 yr of treatment Aigner and Woerly. 2011. Invasive Plant Science and Management 4:448-457 Clethodim, fluazifop, and glyphosate control for barb goatgrass Aigner and Woerly. 2011. Invasive Plant Science and Management 4:448-457 Clethodim, fluazifop, and glyphosate control for barb goatgrass Aigner and Woerly. 2011. Invasive Plant Science and Management 4:448-457 Summary • Midseason application (flower initiation) of clethodim and fluazifop was most effective. Poor at early season (before flowering). • Fluazifop and clethodim increased native forb frequency by 46 and 74%, respectively. • Native perennial grasses were at least partially resistant to the graminicides. • Clethodim and fluazifop show great potential to selectively remove barb goatgrass and other non-native annual grasses in areas otherwise dominated by native grasses and forbs. Preemergence herbicides Control of medusahead with imazapic April application Nov application 70 60 50 40 30 % Cover 20 10 0 Control 2 oz/A 4 oz/A 6 oz/A 8 oz/A 10 oz/A 12 oz/A Plateau rate per acre Kyser, DiTomaso et al. 2008. Weed Technology 21, 66 Response of tilled and untilled plots to imazapic in Yuba 100 Co. Untilled R2 = 0.92, P < 0.0001 80 Tilled R2 = 0.91, P < 0.0001 60 40 Bare ground (%) 20 0 80 60 40 Untilled 20 R2 = 0.71, P = 0.0001 Annualcover (%) grass Tilled R2 = 0.87, P < 0.0001 0 0 1 2 3 Rate of imazapic (oz/A) Kyser, DiTomaso et al. 2008. Weed Technology 21, 66 Summer medusahead cover after first year treatments % cover County Yolo Co. Untreated check 79 a Burn only 11 c Treated 1 oz ae/A 74 a Treated 3 oz ae/A 45 b Burned, treated 1 oz ae/A (4 oz product/ac) 2 c Burned, treated 3 oz ae/A (12 oz product/ac) 0 c Medusahead control Treatments % cover Biomass (g/m2) Roundup (glyphosate) (1 lb product/ac) 4.4 ab 5.2 ab Landmark (sulfometuron + chlorsulfuron) 0 b 0 b Matrix (rimsulfuron) (4 oz product/ac) 0.05 b 0.05 b Plateau (imazapic) (6 oz product/ac) 0.7 b 0.8 b Untreated 11.3 a 10.8 a 2011, post-treatment 2011, pre-treatment Matrix (rimsulfuron) 2016, following two years of control (2011 and 2012) Medusahead control with aminocyclopyrachlor Rate Cover (%) Chemical (oz/acre) medusahead wild oats Method 2 15.1 bc 38.8 Method 4 3.5 c 50.0 Method 6 1.2 c 56.3 Method 8 0.2 c 32.5 Perspective 6.375 6.5 bc 45.0 Matrix 2 25.9 b 50.0 October October 9, 2009 Matrix 4 25.8 b 53.8 Method 2 13.5 27.5 Method 4 6.3 16.3 Method 6 1.2 9.3 Method 8 0.7 13.8 Perspective 6.375 2.3 12.5 March 23, 2010 Matrix 2 13.4 13.8 Matrix 4 11.9 10.8 untreated 39.3 28.8 Method = aminocyclopyrachlor; Perspective = aminocyclopyrachlor + chlorsulfuron; Matrix = rimsulfuron Barb goatgrass Barb goatgrass Other annual grasses Timing Chemical Rate (oz/acre) (% of untreated) (% of untreated) Method October (aminocyclopyrachlor) 8 11.8 467.5 Oct + Jan Method 4 + 4 0.5 358.8 Perspective (aminocyclopyrachlor + Oct + Jan chlorsulfuron) 4 + 4 2.3 242.4 January Method 8 12.7 81.8 January Perspective 8 10.6 142.1 April aminocyclopyrachlor 8 9.2 133.1 none none none 100.0* 100.0* Yellow starthistle cover following two years of control 25 20 a Yuba County 15 ab 10 Percent cover Percent 5 b b b 0 Control Burn/burn Burn/clopyr Clopyr/burn Clopry/clopyr a a b b c c c c c c Conclusions on chemical control • Glyphosate at low rates (6 to 8 oz product/acre) applied at the proper timing (mid- to late season) can be very economical and effective for medusahead control • Clethodim and fluazifop are effective on barb goatgrass, but are best in areas where broadleaves and perennial grasses dominate (e.g., serpentine soils) • Landmark (sulfometuron + chlorsulfuron) gives good control of medusahead for at least one season, but is broad spectrum and will damage other desirable species • Matrix (rimsulfuron) only provides one year of control but multiple years in clay soils can give good long term control of medusahead • Aminopyralid at 14 oz/acre in a spot treatment can give good preemergence control of medusahead and not damage desirable perennial grasses, but is fairly expensive. • Aminocyclopyrachlor at 6 to 8 oz/acre in fall or spring gave excellent control of medusahead and barb goatgrass, but is also fairly expensive. • Integrated approaches, particularly when multiple invasive species are present, may be necessary to achieve the desired outcome. wric.ucdavis.edu Effect of aminopyralid (Milestone), rimsulfuron (Matrix), and imazapic (Plateau) on medusahead cover * Control with aminopyralid A dense medusahead infestation in an untreated plot (left) contrasts with a good stand of Italian ryegrass in a plot treated with 14 oz acre-1 of Milestone in fall (right). .