1. Weed Control in Cover Crops
Brandi C. Woolam
January 23,

2. 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

3. 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

4. Henbit Emergence, Biology, and Control Research
Research conducted in
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

5. 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 F

6. Biology study September 2 WAE October 2 WAE November 2 WAE

7. Henbit Control Five application dates were evaluated: Oct 15 Nov 1
Dec 1
Dec 15
Five Herbicides were evaluated:
Gramoxone 3 pt/A
+ Goal pt/A
+ Valor oz wt /A
+ Dual pt/A
+ oz wt/A

8. 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

9. 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

10. 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
2 oz/A
2 oz/A
32 oz/A
1.5 oz/A

11. 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

12. 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

13. 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:
labeled rate
1 lb ae/A
lb ae/A

14. 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

15. Thank You Questions?