1. Weed management in alfalfa Mark J. Renz mrenz@wisc.edu University of Wisconsin-Madison

3. Reduction in biomass of desirable plants (FEED)

4. Reduction in quality of feed

5. Affect animal healthPoison Reduced feeding

6. Impact of Common Weeds on Forage Quality SERIOUS MODERATE SLIGHT ANNUAL WEEDS . YELLOW FOXTAIL GREEN FOXTAIL COMMON RAGWEED GIANT FOXTAIL VELVETLEAF PIGWEED SPECIES GIANT RAGWEED SHEPHERD’S PURSE SMARTWEEDS PENNYCRESS COCKLEBUR LAMBSQUARTERS NIGHTSHADES WILD MUSTARD PERENNIAL WEEDS . CURLY DOCK CANADA THISTLE DANDELION HOARY ALYSSUM QUACKGRASS WHITE COCKLE YELLOW ROCKET

9. Spring

10. Late summer

12. Reduction in alfalfa plant density from weed competition

13. 55 stems/square foot= 4-5 plants/square foot

14. Goal is for >30 plants/square foot by fall

15. Effects of seeding rate when don’t control weeds

16. Summary for establishment effects on alfalfa density Weeds can reduce stand density Be careful especially if planting Planting lower alfalfa densities Have high weed pressure Competitive weeds species in field Dry conditions that reduce alfalfa emergence Management can alleviate some of the loss Many tools available Allow for scouting and POST application

17. When should we manage weeds in Alfalfa?

18. Critical period Period of time after crop emergence that will not have yield reduction if weeds are removed % alfalfa yield (vs no weeds)

19. Critical period Note can change if more weeds! % alfalfa yield (vs no weeds)

21. 3-5 weeks after planting

22. 1-5 weeks after planting

23. Same period was found for first harvest and first year yield of ALFALFA ONLY

25. Yield changes from weed removal

26. Yield changes from weed removal

27. Yield differences in establishment year5 states including Wisconsin

28. Forage quality (RFV) changes from weed management Can reduce RFV below recommendations for Dairies Depends on the weed species and weed density!

29. Impact of Common Weeds on Forage Quality SERIOUS MODERATE SLIGHT ANNUAL WEEDS . YELLOW FOXTAIL GREEN FOXTAIL COMMON RAGWEED GIANT FOXTAIL VELVETLEAF PIGWEED SPECIES GIANT RAGWEED SHEPHERD’S PURSE SMARTWEEDS PENNYCRESS COCKLEBUR LAMBSQUARTERS NIGHTSHADES WILD MUSTARD PERENNIAL WEEDS . CURLY DOCK CANADA THISTLE DANDELION HOARY ALYSSUM QUACKGRASS WHITE COCKLE YELLOW ROCKET

31. earlier if high weed density

33. Controlling volunteer wheat in summer seeding alfalfa alfalfa no-till drilled at 13 lbs/A 8/18/2008 8/15/2009 Densities wheat 12-49 plants /ft2 7-94 plants /ft2 Mid September Poast at 1.5 pt/A to ½ of the plots. Wheat: 6-8 inches tall Alfalfa 4-6 trifoliate leaves 4-5 inches tall

34. Response of alfalfa density and yield from volunteer wheat 2008-09 = 12- 49 plants/ft22009-10 = 7-94 plants/ft2 4-5 plants/ft2 is minimum threshold, but would like to have 30 plants/ft2

35. Response of alfalfa density and yield from volunteer wheat

36. Does volunteer wheat reduce establishment and yield? ESTABLISHMENT: Yes; 3 to 5 more plants/ft2 in untreated plots than treated. YIELD: Total yield is higher in untreated (42-69%), but % alfalfa can be reduced. FORAGE QUALITY: Untreated reduced quality needed for dairies.

38. weed species and density

39. soil moisture

40. Need for high quality forage

41. Many herbicide options available

42. Scout carefully for weed species/density Alfalfa density/stand establishment

48. >55 stems/sq. ftIf below consider crop rotation Do spring and fall alfalfa counts

49. What herbicide options do I have during establishment?

51. Early postemergence application

52. Alfalfa with it’s second trifoliate leaf or >

53. Weeds 1 to 3 inches tall

54. Raptor better on lambsquarters + foxtails

55. Some injury can occur to alfalfaCan reach 20% yield reduction

57. Each application:

58. no more than 1.5 lbsae/A

59. Over the entire year:

60. No more than 4.64 lbsae/A per year

61. Applications must be at least 7 days apart

63. Costs and benefits of Roundup Ready alfalfa Benefits: herbicide is cheap Roundup ($5-10) vs Pursuit/Raptor ($15-21) Application timing is flexible to crop, but 1 application needed Avoid potential yield loss from standard treatments Can apply to larger weeds and eliminate Control ALS resistant weeds Convenient Costs: Expensive $125/50 lbs bag technology fee Seed costs will be 2x nonproprietary varieties Will need to make a herbicide application No residual weed control May increase potential for glyphosate resistant weeds Future litigation and regulation?

65. Subsequent total yield through the first three production years did not differ

67. Persistence in WisconsinData from Michigan suggests no increase in stand longevity Current research monitoring stand density of older fields

69. Values are pre-entered that reflect Wisconsin’s the costs, use patterns, and yield.

70. User can change data specific for a field or farm and provide a more accurate analysis of the costs. http://www.uwex.edu/ces/forage/pubs/economics_RR_alfalfa.xls

71. What ADDITIONAL herbicide options do I have in established crops? * For common crops (Corn, Soybeans, wheat)

73. Questions? mrenz@wisc.edu