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Weed Management Weed Management in Alfalfain Alfalfa
Fabián MenalledCropland Weed Specialist
719 Leon Johnson HallMontana State University
Weed Management in AlfalfaWeed Management in Alfalfa
Management Management PracticesPractices
EnvironmentEnvironmentInte
grate
d
Integra
ted
Integrated Weed Integrated Weed ManagementManagement
• 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"
Weed Management in AlfalfaWeed Management in Alfalfa
Integra
ted
Integra
ted
• Pre-Crop Pre-Crop • Alfalfa Alfalfa
EstablishmentEstablishment• Established standEstablished stand
Pre-CropPre-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)
Perennial Weeds, Life Perennial Weeds, Life CycleCycle
Canada Thistle Canada Thistle ManagementManagement
Bud Stage Rosette Stage
Cultivated fallow 25 25
Fallow + Banvel (1.05 pt/A)
16 2
Fallow + Banvel (1.1 qt/A)
14 3
no. / m2
Perennial Weeds Perennial Weeds ManagementManagement
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
Alfalfa EstablishmentAlfalfa 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
Alfalfa EstablishmentAlfalfa Establishment
Weed Management Options:
– Mechanical: disking, cultivation
– Chemical Control
•PPI
•Post
Weed Management Weed Management HandbookHandbook
Available: December 2004On-line
Extension PublicationsMontana State UniversityP.O. Box 172040Bozeman, MT 59717-2040
406-994-3273
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
Balan DF
• PPI• 2-2.5 lb/A• annual grasses
– Bluegrass, ryegrass, foxtails, panicums
• broadleaf weeds– Chickweed,
pigweed, lambsquarter, purslane,
Postemergence. Huntley, MTPostemergence. Huntley, MTWeed Control (6/15/01)
1 All Raptor treatments contained COC + 32% UAN
2 Grass = composed of green and yellow foxtail and barnyardgrass
Treatment1
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
Rate------------------ % ------------------
89 94
94 87 97 86
Kochia
91 96
95 95 87 87
Pigwd
91 93
89 88 94 87
Lambsq Grass2
88 98
97 97 51 62
Established AlfalfaEstablished Alfalfa
Is it worth to manage weeds?
Mature alfalfa crowns can compensate for fewer plants by producing more stems or shoots per plant
Is it Worth to Manage Is it Worth to Manage Weeds?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
Herbicides Labeled for AlfalfaHerbicides 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.
Herbicides Labeled for AlfalfaHerbicides 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
Rate Alfalfa Injury Weed Control
7-May 28-Jun 7-May 28-Jun
Velpar Alfamax 0.666 lb/a 6 0 96 100
Velpar Alfamax 1.0 lb/a 21 5 100 100
Sencor 0.666 lb/a 7 0 94 97
Rounup UltraMax 20 oz/a 25 19 82 53
Velpar Alfamax + Karmex
0.66 + 0.75 lb/a 12 1 100 100
Velpar Alfamax + Karmex 1.0 + 1.1 lb/a 14 7 99 100
Velpar Alfamax + Karmex 2.0 + 2.2 lb/a 36 18 99 100
Downy Brome Control in Established Downy Brome Control in Established AlfalfaAlfalfa Fowler Creek, Bozeman, MTFowler Creek, Bozeman, MT
Weeds to WatchWeeds to Watch• Hoary alyssum (Berteroa incana)
The Prairie Star, Sept. 2004
Stevens County Noxious Weed
Larimer Co., CO
Weeds to WatchWeeds to WatchHoary 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