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Weed Management in Alfalfa

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  1. Weed Management in Alfalfa Fabián Menalled Cropland Weed Specialist 719 Leon Johnson Hall Montana State University menalled@montana.edu 406-994-4783

  2. Integrated Management Practices Environment Weed Management in Alfalfa

  3. Integrated Weed Management • Set of cultural, mechanical, and chemical control practices to • Limit the introduction and spread of weeds • Help the crop compete with weeds • Keep weeds "off balance"

  4. Integrated Weed Management in Alfalfa • Pre-Crop • Alfalfa Establishment • Established stand

  5. Pre-Crop • Start NOW your 2006 weed management plant • “Grassy” crop in 2005 (annual summer or winter crop) • Good weed control through alternative herbicides • Break down the sod • “Hay” Barley could be an option to maintain the forage base • Control all perennial weeds the season before planting • Roundup, 2,4-D, dicamba, Curtail, etc. (observe plant-back restrictions to alfalfa)

  6. Perennial Weeds, Life Cycle

  7. Canada Thistle Management no. / m2

  8. Perennial Weeds Management PREPLANT • Roundup Ultra: many species • Eptam: quackgrass, bermudagrass POSTEMERGENCE • Select: foxtail barley, bermudagrass, quackgrass • Buctril: Canada thistle • Basagran: Canada thistle ESTABLIHED ALFALFA • Kerb: foxtail barley, quackgrass, • Velpar: foxtail barley, quackgrass, • Sencor: foxtail barley, chickweed, dandelion, curly dock

  9. Alfalfa Establishment Growing Alfalfa for Hay - Montguide 8505 Alfalfa Variety Selection – Montguide 9303 Alfalfa seedlings are poor competitors Seedbed should be weed free Used weed-free seeds of the highest quality

  10. Alfalfa Establishment Weed Management Options: Mechanical: disking, cultivation Chemical Control PPI Post

  11. Weed Management Handbook Available: December 2004 On-line Extension Publications Montana State University P.O. Box 172040 Bozeman, MT 59717-2040 406-994-3273

  12. Eptam (EPTC) • PPI • 2.25 to 4.5 pt/A • annual grasses • Foxtails, panicum, bromus, small grains, wild oat • broadleaf weeds • Chickweed, pigweed, lambsquarter, purslane, carpetweed

  13. Balan DF • PPI • 2-2.5 lb/A • annual grasses • Bluegrass, ryegrass, foxtails, panicums • broadleaf weeds • Chickweed, pigweed, lambsquarter, purslane,

  14. Kochia Grass2 Lambsq Pigwd Treatment1 Rate ------------------ % ------------------ Raptor Raptor Raptor Poast Pursuit Buctril 2,4-DB 4 fl oz/A 6 fl oz/A 4 fl oz/A 1.5 pt/A 4 fl oz/A 1.5 pt/A 3 pt/A 89 94 94 87 97 86 91 93 89 88 94 87 91 96 95 95 87 87 88 98 97 97 51 62 Postemergence. Huntley, MT Weed Control (6/15/01) 1 All Raptor treatments contained COC + 32% UAN 2 Grass = composed of green and yellow foxtail and barnyardgrass

  15. Established Alfalfa Is it worth to manage weeds? Mature alfalfa crowns can compensate for fewer plants by producing more stems or shoots per plant

  16. Is it Worth to Manage Weeds? Select 3 to 4 two-square-foot sections (17” x 17”) Count the number of stems and divide by two 55 or more stems/ft2 = no change in yield potential with new stand 40-55 stems/ft2 = expect some yield reduction as stand declines <39 stems/ft2 = significant decline or reduction in yield – best option may be to reestablish

  17. Herbicides Labeled for Alfalfa • Sinbar – 0.5 to 1.5 lbs/A. Grassy and broadleaf weeds. Do not apply on frozen soil. • Treflan - 1.5 to pts / A. Do not apply to seedling alfalfa. • Velpar - 1 to 2 qts / A. Rates vary with soil characteristics. Do not graze within 30 days.

  18. Herbicides Labeled for Alfalfa • Velpar – Alfamax • Combination of Diuron and Velpar (hexazinone) • Dry flowable • Contact and residual control • One single application during winter • Rates = 3.3 – 10 Acres / Unit Pack (14.2 pounds), depending on soil texture and organic matter • Mustards, pigweed, chickweed, common lambsquarters • Branyardgrass, cheatgrass • Dry bulk fertilizer may be coated with Velpar - Alfamax • Caution: can damage trees and shrubs

  19. Downy Brome Control in Established AlfalfaFowler Creek, Bozeman, MT

  20. Stevens County Noxious Weed Weeds to Watch • Hoary alyssum (Berteroa incana) The Prairie Star, Sept. 2004 Larimer Co., CO

  21. Weeds to Watch Hoary alyssum • Toxic to livestock • Up to two feet tall • Large number of seeds • No Biological Control Options • Mechanical Control • Hand-pulling of small populations. • Mowing will not control it • Chemical Control • Tordon + 2,4-D amine • Redeem • Curtail