ALFALFA WEED CONTROL

ROB WILSON and STEVE ORLOFF

University of California Cooperative Extension

Seedling Alfalfa Weed Control

• Perfect seedbed conditions for weed establishment

• Alfalfa seedlings are slow to establish and very vulnerable to weed competition

• 1st cutting can be over 50% weeds if weeds aren’t controlled

• Weed competition can reduce alfalfa stands!

Timing Herbicide Grass

Control

Broadleaf

Control

Crop

Safety Preplant

Post to weed

Roundup

Paraquat

Y

Y

Y

Y

E

E

Preplant

Pre to weed

Balan (benefin)

Eptam (EPTC)

Y

Y

Y

Y

E

G

Postplant

Post to weed

and alfalfa

2,4-DB

Buctril (bromoxynil)

Select (clethodim)

Roundup (GT alfalfa only)

Raptor (imazamox)

Pursuit (imazethapyr)

paraquat

Poast (sethoxydim)

N

N

Y

Y

Y

Y/P

Y

Y

Y

Y

N

Y

Y

Y

Y

N

G

F/G

E

E

G

G

F

E

Postplant Newly

established

Velpar (hexazinone)

Paraquat

Y

Y

Y

Y

F

F

Herbicides for Seedling Alfalfa

Red font indicates most popular in Western states.

Broadleaf Weeds

Kochia

Henbit

Mustards

Prickly Lettuce

Lambsquarters

Groundsel

Fiddleneck

Filaree

Dock, Curly

Common Mallow

Chickweed

Buctril 2,4-DB Pursuit Raptor

Pursuit vs. Raptor Pursuit

• 40% cheaper than Raptor

• Less crop injury on spring-planted alfalfa compared to Raptor

• Less crop injury on established alfalfa

• Use with a methylated seed oil for best control

Raptor

• Controls several grass weeds

• Better control of henbit & lambsquarter compared to pursuit

• Use with a methylated seed oil for best control

Can’t Decide: • Tank-mix the low rate of Pursuit with the low rate of Raptor • Tank-mix Buctril with Pursuit or Raptor to control prickly lettuce and fiddleneck • Tank-mix Select with Pursuit to control grasses

Application Timing Effect on London Rocket Early: 2-3 leaves Late: 4-6 leaves (1 month difference)

0 50 100

2,4-DB .5

2,4-DB .75

Buctril .25

Buctril 0.5

Pivot .063

Pivot .094

% Control

Late

Early

Pursuit

Pursuit

Established Alfalfa Weed Control

• Established alfalfa is great competitor with weeds

• If you have a lot of weeds, ask yourself why?

• Control weeds that emerge in fall or late winter before alfalfa greens up in the spring

• Control weeds that emerge after cutting or in areas where the alfalfa stand is thin

Herbicides for Established Alfalfa • Velpar + Gramoxone or Sencor + Gramoxone applied in

February or early March before spring greenup are the best option for winter annual weeds in the Intermountain region

• Flumioxazin (Chateau) is a newer option for winter weed control; It hasn’t proven superior to Velpar for the spectrum of weeds we have in Tulelake.

0

2000

4000

6000

8000

10000

12000

14000

Acr

es

Tre

ate

d

20022012

Herbicide Use in Siskiyou County in 2002 Versus 2012

Velpar vs. Metribuzin (Sencor)

Velpar

• Better control of bluegrass, emerged grasses, knotweed, and groundsel

• Better suppression of larger emerged weeds

• Longer residual

Metribuzin

• 50% cheaper than Velpar

• Less residual and plant-back restrictions compared to Velpar

• Labeled for alfalfa-grass mixtures

Tansy Mustard Control in

Established Alfalfa

0 20 40 60 80 100

Chateau

Chateau + Gramoxone

Velpar

Sencor

Raptor

Gramoxone .375

Gramoxone 0.5

Chateau

Chateau + Gramoxone

Sencor

Sencor + Gramoxone

Velpar

Velpar + Gramoxone

Control (%)

10/16

2/19

Shepherd’s Purse Control

in Established Alfalfa

0 20 40 60 80 100

Chateau

Chateau + Gramoxone

Velpar

Sencor

Raptor

Gramoxone .375

Gramoxone 0.5

Chateau

Chateau + Gramoxone

Sencor

Sencor + Gramoxone

Velpar

Velpar + Gramoxone

Control (%)

2/19

10/16

Downy Brome Control in

Established Alfalfa

0 20 40 60 80 100

Chateau

Chateau + Gramoxone

Velpar

Sencor

Raptor

Gramoxone .375

Gramoxone 0.5

Chateau

Chateau + Gramoxone

Sencor

Sencor + Gramoxone

Velpar

Velpar + Gramoxone

Control (%)

2/19

10/16

Product

rate1

Shepherdspurse2

Yellow foxtail3

Lambsquarter4

pint / acre ---------------------- % control -------------------- Untreated -- 0 0 0

Gramoxone Inteon5 2 42 0 0 Prowl H20 +

Gramoxone Inteon

3 + 2 47 51 63

Prowl H20 +

Gramoxone Inteon

4 + 2 40 93 91

Prowl H20 +

Gramoxone Inteon

6 + 2 53 96 97

Prowl H20 +

Gramoxone Inteon

8 + 2 53 100 100

Velpar L +

Gramoxone Inteon

1.5 + 1 100 67 85

Prowl H20 + Velpar L

+ Gramoxone Inteon

4+1.5+1 100 100 100

Prowl H20 + Velpar L 4 + 2 100 97 100 Prowl H20 + Velpar L 6 + 2 100 98 97 Sencor 4SC +

Gramoxone Inteon

0.75 + 1 100 0 88

Prowl H20 + Sencor

4SC + Gramoxone

Inteon

4+0.75+1 100 92 97

Karmex 80DF +

Gramoxone Inteon

1.9 lb +

1.5 97 42 77

Prowl H20 + Karmex

80DF + Gramoxone

Inteon

4 + 1.9 lb

+1.5 93 98 98

Prowl H20 + Sencor

4SC + Karmex 80DF

+ Gramoxone Inteon

4 + 0.75 +

1.9 lb +1 98 98 98

LSD (0.05) 17 12 13

Prowl H20

• Pre-emergent Herbicide- Apply in late winter or early spring before summer weeds emerge; it can be mixed with Velpar or Sencor trts

• Must be incorporated in the soil with rain or irrigation before weeds emerge! Low water solubility

• Controls most summer annual grasses

• Suppresses pigweed, lambsquarter, knotweed, and Russian thistle

Non-Chemical Weed Control Tools • Seedling Alfalfa

– Fall vs. Spring Seeding Date • What weeds are a problem in the field? Winter weeds try

spring seeding; summer weeds try fall seeding

– Pre-irrigation – good option for organic alfalfa production

– Early cutting can minimize weed seed production

• Established Alfalfa – Cutting schedule- longer period between cuttings

usually results in less weeds – Spring harrowing- works well for controlling seedling

broadleaves – Overseed grass into old stands (orchardgrass, oats, etc.)

Weed Management with Roundup Ready Alfalfa

Steve Orloff

Farm Advisor

UCCE Siskiyou County

The most effective non-selective herbicide available

Controls a broader spectrum of annuals and perennials than any other herbicide

Level of Grower Satisfaction with RR Alfalfa

0

10

20

30

40

50

60

70

Far ExceededExpectations

Very Pleased Satisfied Disappointed ExtremelyDisappointed

Nu

mb

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of

Re

spo

nd

en

ts

Would you plant RR again? 72% Yes 21% Maybe 7% No

What Have You Liked Most About RR Alfalfa?

0 10 20 30 40 50 60 70

Haven't really liked it at all

Cost effectiveness

Higher yields/quality or stand persistence

Flexibility in application timing

Simplicity in weed management

Better weed control

Frequency of Response (%)

Major Negatives Associated with RR Technology

0 10 20 30 40 50 60 70 80 90

Difficulties in marketing RR alfalfa

Varieties don't seem to yield well

I don't like the technology-useagreement

None, there were no negatives

Roundup-resistant weeds

Weed control was not effective

Cost of RR alfalfa seed

Frequency of Response (%)

Pursuit + Buctril Roundup

Crop Injury

Crop Injury

0 5 10 15 20 25

RU 1 unifol

RU 1 3-4

RU 1 6-9

RU 2 3-4

RU 2 6-9

Pursuit+Buct 3-4

Raptor 3-4

Pursuit+Buct 6-9

Roundup Glyphosate

Raptor Imazamox

Established Alfalfa Trials

• Quackgrass • Dandelion • Bermudagrass • Nutsedge • Field Bindweed • Perennial Pepperweed • Curly Dock • Canada Thistle

Roundup Ready Alfalfa allows for control of Perennial Weeds!!

Glyphosate 1 lb a.i. acre

Fall and Spring

Klamath Basin 2005

Evaluation Poor Weed Control

Untreated Roundup .75 ae

Applied 0ct 2002 Iowa Quackgrass trial

9 months AA

Untreated

.94 AE

WeatherMax 1.5AE WeatherMax

Dandelion trial, Iowa One application Fall applied to 3-4 leaf Alfalfa 7 months AA

Flexibility of RR System

RR Alfalfa – Important Questions/Cons

Roundup does not control all weeds (cheeseweed, filaree, nettle)

Resistant weeds: Ryegrass and Marestail

Roundup Ready Alfalfa Variety

Yields?

• Conventional and GT alfalfa cultivars were seeded on June 7, 2005 at

the Intermountain Research and Extension Center (IREC) in Tulelake,

California.

• Twelve conventional varieties plus a standard check variety (Vernal)

• Treated with conventional herbicides

• Twelve GT varieties (6 are now commercial varieties and 6

experimental varieties)

• One block treated with conventional herbicides

• One block treated with glyphosate

• Yield data collected from all harvests from 2005 through 2009

• Two cuttings in seeding year

• Four cuttings in each subsequent year

Effect of Herbicide Treatment on Yield of GT Alfalfa Tulelake, CA (Ave. 2005-2009)

15

15.5

16

16.5

17

17.5

18

Yie

ld (

Mg

ha-1

)

Glyphosate

Conventional

LSD (0.05) = 0.74

Variety Genetic Background

Herbicide Applied 2005 2006 2007 2008 2009

5-Year Average % of Vernal

R54BD14 GT Glyphosate 10.00 23.75 19.02 17.48 19.08 17.87 111.9 Legendairy Conv. Conventional 9.86 24.08 19.78 16.99 18.50 17.85 111.7 Expedition Conv. Conventional 9.55 23.06 19.06 17.67 18.63 17.60 110.2 R54BD17 GT Glyphosate 9.87 23.75 19.18 16.22 18.80 17.56 110.0 Rebound Conv. Conventional 10.07 22.94 19.28 16.67 17.71 17.33 108.5 RR405 GT Glyphosate 9.45 23.03 18.46 16.60 19.00 17.31 108.4 R44BD13 GT Glyphosate 9.65 22.89 19.29 16.39 18.02 17.25 108.0 R54BD17 GT Conventional 8.81 22.95 18.55 17.29 18.48 17.22 107.8 DKA43-22RR GT Glyphosate 10.12 22.88 18.72 15.65 18.63 17.20 107.7 RR405 GT Conventional 8.79 22.43 18.44 17.30 18.30 17.05 106.8 WL 357HQ Conv. Conventional 9.24 22.31 19.53 16.83 17.33 17.05 106.8 Boulder Conv. Conventional 10.42 22.47 18.08 15.95 17.93 16.97 106.2 Hybriforce 400 Conv. Conventional 11.79 21.89 17.46 15.11 18.63 16.97 106.3 Ameristand 405T RR GT Conventional 9.42 22.06 17.64 18.05 17.66 16.97 106.3 R54BD14 GT Conventional 9.35 21.99 18.90 17.26 17.21 16.95 106.1 Innovator +Z Conv. Conventional 10.01 22.40 18.22 15.28 18.80 16.94 106.1 R43M625 GT Glyphosate 9.79 22.66 19.01 15.60 17.60 16.93 106.0 Masterpiece Conv. Conventional 10.79 22.37 17.68 15.80 17.79 16.88 105.7 Ameristand 405T RR GT Glyphosate 9.70 21.04 18.14 16.75 18.79 16.88 105.7 R44BD06 GT Conventional 8.71 22.20 18.83 16.46 18.18 16.88 105.7 WL355RR GT Glyphosate 10.42 21.87 18.42 15.86 17.82 16.87 105.7 Mountaineer Conv. Conventional 9.83 22.92 17.84 16.42 17.14 16.83 105.4 R44BD06 GT Glyphosate 9.55 22.27 18.45 15.74 18.03 16.81 105.3 R44BD09 GT Glyphosate 9.79 22.36 18.07 15.84 17.85 16.79 105.1 54R01 GT Conventional 9.36 22.48 18.21 16.97 16.90 16.78 105.1 Dura 512 Conv. Conventional 10.54 22.73 17.81 15.44 17.34 16.77 105.0 RRALPH 6R100 GT Glyphosate 10.43 21.29 17.86 16.34 17.96 16.77 105.0 R43M625 GT Conventional 9.60 22.12 18.26 16.90 16.92 16.77 104.9 DKA43-22RR GT Conventional 8.80 22.31 18.22 16.69 17.42 16.69 104.5 WL355RR GT Conventional 9.18 22.05 18.62 16.00 17.57 16.69 104.5 54R01 GT Glyphosate 10.12 22.08 17.93 15.88 17.44 16.68 104.5 RRALPH 6R100 GT Conventional 9.74 20.46 18.68 17.12 17.35 16.67 104.4 R44BD13 GT Conventional 9.03 20.61 18.49 17.33 17.70 16.63 104.2 54V54 Conv. Conventional 9.98 21.57 17.69 15.40 17.66 16.46 103.1 R44BD09 GT Conventional 8.60 20.62 18.35 16.84 16.66 16.22 101.5 Ameristand 403T Conv. Conventional 10.15 20.31 17.88 14.72 17.67 16.14 101.1 Vernal Conv. Conventional 10.18 20.61 16.54 14.59 17.94 15.97 100.0

0.00 0.00 0.00 0.00 0.00 0.00 Mean 9.75 22.21 18.39 16.36 17.90 16.92 LSD (P<0.05) 0.78 2.02 1.07 1.36 1.15 0.73 CV 5.70 6.49 4.15 5.92 4.58 3.07

Forage Quality of 10 RR and 22 Conventional Alfalfa Varieties

Tulelake, 2011 (1st Cut)

0

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60

CP ADF NDF TDN

Co

nce

ntr

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n (

%)

Forage Quality Parameter

Conventional

RR

Is RR alfalfa worth the extra seed cost?

• Technology fee is added to the cost of seed

• I’d say yes in field situations with perennial weed problems or field situations you’ve had trouble getting effective weed control with conventional herbicides