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 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 Dean Lee Research and Extension Center

Henbit Emergence All locations-Henbit Emergence 2011-2015 Blackshaw et. al 2002 research Soil temperature – 5-25 C with greatest emergence at 59 to 68 F Louisiana survey Soil temperature - largest emergence peaks at 50-65 F

Biology study September 2 WAE October 2 WAE November 2 WAE

Henbit Control Five application dates were evaluated: Oct 15 Nov 1 Dec 1 Dec 15 Five Herbicides were evaluated: Gramoxone SL @ 3 pt/A + Goal 2XL@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 2XL 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 LeadOff @ 1.5 oz/A

Winter Weed Control and cover Crop tolerance Cereal rye tolerant of Zidua, Valor, and Boundary. LeadOff resulted in severe stand and ground cover reductions Tillage radish only tolerant of Zidua. Zidua had very little impact on tillage radish growth Crimson Clover only tolerant of Zidua. 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?