Weed Management Weed Management in Alfalfain Alfalfa

Fabián MenalledCropland Weed Specialist

719 Leon Johnson HallMontana State University

menalled@montana.edu406-994-4783

Weed Management in AlfalfaWeed Management in Alfalfa

Management Management PracticesPractices

EnvironmentEnvironmentInte

grate

d

Integra

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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

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• 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