Effect of Various Herbicides on Switchgrass Establishment Chengjun Huo, Twain J. Butler, Jimmy D. Stein and Sindy M. Interrante The Samuel Roberts Noble Foundation Forage Improvement Division 2510 Sam Noble Parkway Ardmore, OK 73401

Introduction Switchgrass (Panicum virgatum L.) is a perennial warm-season (C4) forage grass native to most of North American with:  Broad adaptation to wide range of soil pH (5-8))  High biomass yield (h igher N and water use efficiency)  Low production cost  Environmental benefits (e.g. soil erosion control, organic matter enrichment, enhancement of wildlife habitat)  Establishment of switchgrass is slow and difficult, is a major limitation for its widespread use :  Seed is very small  Growth slow during early seeding year  Affected by weeds competition  Improving rate of speed of establishment will increase production and utilization  Only a few herbicides have been labeled for use on switchgrass

Objective  Determine herbicides (PRE and POE) can selectively remove weed competition and improve establishment of switchgrass Switchgrass – Cave-in-Rock Switchgrass – EG 1101

Materials and Methods  Field experiment (RCBD with 4 replications in 2009),  Various herbicides: PRE: FirstRate, Strongarm, Siduron POE: Dual, Prowl, Dimension, Accent, Raptor, MSMA, Paramount, Option and Stam  Two switchgrass ecotypes Upland type cultivar :Cave-in-Rock Lowland type line: EG1011  Grassy weeds planted: Broadleaf signalgrass (BLSG), Crabgrass (CG), Johnsongrass (JG), Giant Foxtail (GFT) and TX panicum (TXPAN)  Switchgrass and grassy weeds were planted in spring and treated with both PRE, post-emergence (POE) and PRE followed by POE herbicides on sandy soil (at 1-2, 2-3 and 4-5 leaf stage)  Data recorded for injury at 30, 60 and 90 days after treatment (DAT) and percent coverage at the end of season.

Results

2009 Pre and 1-2-leaf stage (only) – EG1101 Injury % Injury PRE trts. 1-2-leaf

2009 Pre and 1-2-leaf stage (only) – CaveInRock Injury % Injury PRE trts. 1-2-leaf

Pre and 1-2-leaf stage only – Weed control 30 DAT - RR PRE trts. 1-2-leaf

Pre and 1-2-leaf stage only – Coverage- RR PRE trts. 1-2-leaf

leaf stage only –– EG1101 Injury % Injury

leaf stage only –– CaveInRock Injury % Injury

2-3-leaf stage only – Weed control 30 DAT - RR

Accent Controlled Johnsongrass, signalgrass, and foxtail 13

leaf stage only – % Coverage

FirstRate Pre fb POE herbicide treatments – EG1101 Injury - RR 1-2-leaf stage 2-3-leaf stage

FirstRate Pre fb POE herbicide treatments –CaveInRock Injury - RR 1-2-leaf stage 2-3-leaf stage

FirstRate Pre fb POE herbicide treatments – Weed control 30DAT - RR 1-2-leaf stage 2-3-leaf stage

FirstRate Pre fb POE herbicide treatments – Coverage - RR 1-2-leaf stage 2-3-leaf stage

FirstRate fb Paramount Controlled Crabgrass 19

4-5leaf stage only – EG1101 Injury - RR

4-5leaf stage only – CaveInRock Injury- RR

4-5leaf stage only – Weed Control- RR 30DAT 60DAT

FirstRate Pre fb POE herbicide treatments and 4-5leaf – Coverage - RR

 PRE Herbicides FirstRate suppressed crabgrass,caused lower injury and resulted in higher switchgrass coverage. Tupersan (siduron) and Strongarm (diclosulam) caused excessive switchgrass injury.  POE 1-2 leaf stage: Dual, Prowl, Dimension were safe on both lowland and upland switchgrass but did not control grassy weeds. Accent, Raptor, MSMA, and Stam generally controlled grassy weeds, but caused excessive switchgrass injury. Paramount (quinclorac), was safe on both upland and lowland switchgrass. Option (foramsulfuron) was relatively safe on lowland switchgrass. PRE plus POE (1-2-leaf) FirstRate fb Paramount was safe on switchgrass and suppressed crabgrass. FirstRate fb MSMA controlled all grassy weeds, but also killed switchgrass. Discussion

 POE 2-3 leaf stage: Raptor and Stam caused excessive switchgrass injury. Outrider and Option were relatively safe on switchgrass, but only controlled Johnsongrass. Paramount was relatively safe on switchgrass, but grass control was erratic. Accent, MSMA, Accent/Prowl, Accent/Paramount mixtures caused severe injury, although lowland switchgrass generally recovered.  PRE plus POE (2-3-leaf) FirstRate fb Paramount was generally safe on both switchgrass ecotypes and suppressed crabgrass, broadleaf signalgrass, and foxtail. FirstaRate fb Raptor, and FirstRate fb Accent caused excessive switchgrass injury. FirstRate fb MSMA controlled most grassy weeds and caused severe injury, but lowland switchgrass recovered by end of season.  4-5 leafe stage: Delayed weed control (after 4-leaf stage) resulted in poor switchgrass coverage.

Conclusion Herbicides that may increase lowland switchgrass establishment –FirstRate PRE to suppress crabgrass. –Paramount 1-2 leaf stage to suppress broadleaf signalgrass and crabgrass –Prowl H2O 1-2 leaf stage to provide residual grass control –Option 1-2 leaf stage to control Johnsongrass and foxtail –Accent 2-3 leaf stage to control most grassy weeds except TX panicum –MSMA 3-4 leaf stage to control most grassy weeds 26

Future Research Validate selected herbicides across multiple environments (sand, clay, high soil pH, low soil pH) 27