Weed Control in Cover Crops Brandi C Woolam
Weed Control in Cover Crops Brandi C. Woolam January 23, 24 2018
Rational for Research • Cover crops can provide several agronomic benefits • Waiting till the spring to burndown weeds can lead to control failures • Fall applied soil residual herbicides provides good winter annual weed control into early spring • Can we use fall applied soil residual herbicides in cover crops and maintain adequate cover for NRCS programs • When and how do we terminate cover crops
Winter Annuals • Producers often control winter annual weeds in spring with herbicide applications • Poor control reported by Louisiana crop producers with spring-applied herbicides, specifically Henbit • Uncontrolled winter annuals may interfere with crop planting, growth, and development via direct competition or through harboring of other pests
Henbit Emergence, Biology, and Control Research • Emergence – Research conducted in 2011 -2015 • Northeast Research Station in St. Joseph, LA • Producer’s farm in Concordia Parish, LA • Dean Lee Research and Extension Center in Alexandria, LA • Ben Hur Research Station in Baton Rouge, LA • Biology and control study – Research conducted in 2011 -2015 • Dean Lee Research and Extension Center
Henbit Emergence All locations-Henbit Emergence 2011 -2015 8000 Blackshaw et. al 2002 research 7000 5000 Soil temperature – 5 -25 C with greatest emergence at 59 to 68 F 4000 Louisiana survey 3000 Soil temperature - largest emergence peaks at 50 -65 F 2000 1000 3/9 3/2 2/24 2/17 2/10 2/3 1/27 1/20 1/13 1/6 12/30 12/23 12/16 12/9 12/2 11/25 11/18 11/11 11/4 10/28 10/21 10/14 10/7 9/30 9/23 0 9/16 Total 6 m-2 6000 SJ 2011 SJ 2012 SJ 2013 SJ 2014 TW 2011 TW 2012 TW 2013 TW 2014 DL 2011 DL 2012 DL 2013 DL 2014 BH 2011 BH 2012 BH 2013 BH 2014
Biology study September 2 WAE October 2 WAE November 2 WAE September 12 WAE October 12 WAE November 12 WAE
Henbit Control • Five application dates were evaluated: • Oct 15 • Nov 15 • Dec 15 • Five Herbicides were evaluated: • Gramoxone SL @ 3 pt/A • + Goal 2 XL@1 pt/A • + Valor SX @2 oz wt /A • + Dual Magnum @1. 33 pt/A • + Leadoff @1. 5 oz wt/A
Henbit Control • Application timing made November 1 through December 1 provided the most consistent henbit control. • October 15 and December 15 timings do not provide consistent environments for applying herbicides • warm and dry field conditions in October 15 • colder, wet conditions December 15 • Data indicates Goal 2 XL is the most consistent herbicide for henbit management, providing at least 89% control 100 DAT
• Valor SX and Leadoff are also excellent options for control, density and height reduction when applications are delayed to November 1 and after achieving 90% and greater control 100 DAT. • Dual Magnum is an option for henbit control when applied November 1 through December 1 with 76% control 100 DAT Goal 2 XL applied Nov 15 in late March Valor SX applied Nov 15 in late March Leadoff applied Nov 15 in late March
Winter Weed Control and Cover Crop tolerance • 4 cover crops were evaluated: – – Cereal rye (120 lb/a) Tillage Radish (8 lb/a) Crimson Clover (20 lb/a) Austrian Winter Pea (30 lb/a) • 5 herbicides were evaluated: – – – No herbicide Zidua @ 2 oz/A Valor @ 2 oz/A Boundary @ 32 oz/A Lead. Off @ 1. 5 oz/A
Winter Weed Control and cover Crop tolerance • Cereal rye tolerant of Zidua, Valor, and Boundary. Lead. Off resulted in severe stand ground cover reductions • Tillage radish only tolerant of Zidua had very little impact on tillage radish growth • Crimson Clover only tolerant of Zidua had very little impact on crimson clover growth
Winter Weed Control and cover Crop tolerance • A. winter pea was tolerant to all herbicides. However height and ground cover was reduced by all herbicides except Zidua • Cereal rye (8%) and tillage radish (6%) most effective in reducing weed density compared to crimson clover (20%) and A. winter pea (29%) • There were no corn yield differences between treatments
Termination • When? • Many factors to consider. – What’s the primary purpose of a cover crop for you? – NRCS zone 4. • At or within 5 days of planting, but before crop emergence • Terminate 4 to 6 weeks prior to planting cash crop • Current herbicide recommendations for cover crop termination are: – glyphosate @ labeled rate – 2, 4 -D @ 1 lb ae/A – dicamba @ 0. 25 lb ae/A
Summary • Cover crops can provide several agronomic benefits – Know your winter weed spectrum – Choose your cover crop according to your needs – Preliminary data indicates that cereal rye, crimson cover, tillage radish, and Austrian winter pea are tolerant to Zidua at 2 oz/A – Termination is dependent on multiple factors – Further research is being conducted on cover crops
Thank You Questions?
- Slides: 15