weed control in green peas tim miller wsu mount vernon nwrec

Weed Control in Green Peas

Tim MillerWSU Mount Vernon NWREC

Positive Attributes of Green Peas

• Many herbicides available

• Densely-growing crop competes well with weeds

• Short-season crop

• Lower soil N may decrease weed growth

Preplant-incorporated Herbicides Available for Use

in Green Peas•Treflan (trifluralin)•Far-Go (triallate)•Buckle (trifluralin +

triallate)•Pursuit (imazethapyr)•Prowl (pendimethalin)•Sharpen (saflufenacil)

Preemergence Herbicides Available for Use in Green

Peas•Pursuit (imazethapyr)•Prowl (pendimethalin)•Dual Magnum (s-

metolachlor)•Command (clomazone)•Sencor (metribuzin)•Sharpen (saflufenacil)

Postemergence Herbicides Available for Use in Green

Peas•Pursuit (imazethapyr)•Sencor (metribuzin)•MCPA•MCPB•Basagran (bentazon)•Poast (sethoxydim)•Assure II (quizalofop)

Green Pea Studies• Competitive Ability of Green

Pea• Reduced Rate Herbicide Trials• Stale Seedbed Trials• Spartan and Chateau Trials

(if there is time…)

Pea Interference Study • 'Charo' green pea• Weeds removed from plots

at weekly intervals and kept weed-free until harvest– 1, 2, 3, 4, 5, and 6 weeks after

emergence

• Weedy and weed-free plots

Pea Density and Pea Weight2001-03

0

50

100

150

200

250

300

350

plants/plot 100 pea wt. (g)

Weed free1 week2 weeks3 weeks4 weeks5 weeks6 weeksFull

Pod Production and Pea Yield2001-03

0

1.6

3.2

4.8

6.4

8

pods/plant yield (tons/a)

Weed free1 week2 weeks3 weeks4 weeks5 weeks6 weeksFull

Pea Interference Studies

• Pea plant density slightly reduced by weed interference

• Pea size not reduced by duration of weed interference, but pod number decreased

• No yield loss if weeds were controlled by 5 weeks after emergence

Reduced Rate Herbicide Trials

2001-03• ‘Snake’ pea seeded early May• PRE herbicides applied shortly after seeding• POST herbicides applied late May to early June• Weed control and crop injury estimated• Peas and weeds harvested in late July/early

August– Sampling within a 1 m2 quadrat– Pea yield and plant biomass calculated– Weed biomass calculated– Seeds from weeds germinated in the greenhouse


• Tested herbicides were:– Command, PRE– Sencor, PRE and POST– Basagran, POST– MCPA, POST

• Various combinations of these products were tested at various rates


• Six “full rate” treatments:– Command (1.3 pt/a, PRE)– Sencor (5.3 oz/a, PRE)– Sencor (2.7 oz/a, POST)– MCPA (8 fl. oz/a, POST)– Basagran (1.5 pt/a, POST)– Command + Basagran (1.3 pt/a + 1.5 pt/a, PRE + POST)


• 14 “partial rate” treatments:– Command (11 fl. oz/a, PRE)– Sencor (2.7 oz/a, PRE)– Sencor (1.3 oz/a, POST)– MCPA (4 fl. oz/a, POST)– Basagran (12 fl. oz/a, POST)


• 14 “partial rate” treatments (cont.):– Command + Sencor

• 5.4 fl. oz/a + 1.3 oz/a, PRE

– Command + Sencor• 5.4 fl. oz/a + 0.7 oz/a, PRE + POST

– Command + Basagran• 5.4 fl. oz/a + 12 fl. oz/a, PRE + POST

– Command + MCPA• 5.4 fl. oz/a + 2 fl. oz/a, PRE + POST


• 14 “partial rate” treatments (cont.):– Sencor + Basagran

• 1.3 oz/a + 12 fl. oz/a, PRE + POST

– Sencor + MCPA• 1.3 oz/a + 2 fl. oz/a, PRE + POST

– Sencor + Basagran• 0.7 oz/a + 12 fl. oz/a, POST

– Sencor + MCPA• 0.7 oz/a + 2 fl. oz/a, POST

– Basagran + MCPA• 12 fl. oz/a + 2 fl. oz/a, POST

Pea Yield2001-03

0

1.6

3.2

4.8 Com + Bas

Sen (Hi, PRE)

Com (Hi)

Com + Sen (PRE)

Com + Sen (PRE,POST)Untreated

tons/a

aa

ab abab

g

Biomass Returned to the Field

2001-03

0

1.6

3.2

4.8

Pea dry weight Weed dry weight

Com + Bas

Sencor (Hi, PRE)

Command (Hi)

Com + Sen (PRE)


tons/a

abc

ghihij

j

ijij

ab abca ab

bcd

g

Pea:Weed Biomass Ratios

• Divide the pea biomass by the weed biomass– If ratio is >1.0, more pea

residue than weeds returned

– If ratio is <1.0, more weeds than peas returned

Pea:Weed Biomass Ratio2001-03

0

5

10

15

20 Com + Bas

Sencor (Hi, PRE)

Command (Hi)

Com + Sen (PRE)


a

b

bc cd d d

Common Lambsquarters Germination Counts

2002 only

0

500

1000

1500

2000

Fall Spring Total

Com + Bas

Sen (Hi, PRE)

Com (Hi)

Com + Sen (PRE)


weeds/m2

Pineappleweed Germination Counts2002 only

0

200

400

600

800

1000

Fall Spring Total

Com + Bas

Sen (Hi, PRE)

Com (Hi)

Com + Sen (PRE)


weeds/m2

Shepherd’s-purse Germination Counts2002 only

0

100

200

300

400

500

600

Fall Spring Total

Com + Bas

Sen (Hi, PRE)

Com (Hi)

Com + Sen (PRE)


weeds/m2

Reduced Rate Herbicide Trial—Total Weed Seed Germination

Counts

0

2000

4000

6000

8000

10000

Fall Spring Total

Com + Bas

Sen (Hi, PRE)

Com (Hi)

Com + Sen (PRE)


weeds/m2

• So in this case, return of weed seed to field would have resulted in:– Command + Basagran (PRE + POST)

•3 weeds/m2 (12,000/acre)

– Sencor (PRE)•469 weeds/m2 (1.9 million/acre)

– Untreated check•8055 weeds/m2 (32.6 million/acre)

Weed Seed Germination

Reduced Rate Herbicide Trial

Conclusions, 2001-03• All herbicide treatments resulted in at least 2

tons of harvested peas/a (6 full rates, 14 partial rates)– Based on dry biomass production, only 8 of 20

treatments adequately controlled weeds (4 full rates, 4 partial rates)

– Weed dry biomass in the remaining 12 treatments exceeded pea dry biomass

• Even in a short-season crop like green peas, only 1 of 20 treatments prevented tremendous return of weed seed to the field (full rate of Command + Basagran)

Stale SeedbedAllow weed seeds to germinate, then kill them with herbicide or flame prior to crop emergence

Stale Seedbed Trial Overview

2007-09• Seedbed preparation:

– Two weeks prior to seeding (14 d)– One week prior to seeding (7 d)– Three days prior to seeding (3 d)– Same day as seeding (0 d)

• Seeding dates ( ‘Snake’)– 5/2507, 7/1/08, and 5/21/09


2007-09• PREPO treatments (PRE to pea,

POST to weeds): – Glyphosate (1 lb ae/a, 2 pt/a)– Paraquat (0.75 lb ai/a; 2.4 pt/a)– Glufosinate (0.5 lb ai/a; 4 pt/a)– Pyraflufen (0.004 lb ai/a; 2.5 fl.oz/a)– Flame (propane, open flame)– None


2007-09• PRE treatments (residual herbicides

applied at same time as the PREPO treatments): – Command (0.5 lb ai/a; 1.3 pt/a)– Prowl H2O (1.52 lb ai/a; 3.2 pt/a)– Sencor (0.38 lb ai/a; 8.1 oz/a)– None


2007-09• Herbicide/flame application dates

(days after seeding)– 2007: 8 days– 2008: 5 days– 2009: 16 days

• Years were significantly different, so data are presented separately by year

Stale Seedbed Trial2007 Results

• Weed control at 21 DAT generally good at all seedbed timings– Glyphosate, 93 to 95%– Paraquat, 94%– Glufosinate, 86 to 94%– Pyraflufen, 54% (14 d); 71 to 86%– Flame, 70% (14 d); 83 to 88%– None, 0% (14 d); 60 to 76%

• By harvest, weed control was poor to good

Weed Control At Pea HarvestJuly, 2007

0

20

40

60

80

100

0 d 3 d 7 d 14 d

GlyphosateParaquatGlufosinatePyraflufenFlameCheck

%

80% 83% 78%

67%


• Green pea vine and pod fresh weight were not greatly affected by herbicide choice (ranged from 3.46 kg/m2 for no herbicide to 3.90 kg/m2 for glyphosate)

• Seedbed timing made no significant difference on green pea vine and pod fresh weight (3.54 to 3.79 kg/m2)

Weed Control At Pea Harvest September, 2008

0

20

40

60

80

100

0 d 3 d 7 d 14 d


%

86% 79% 83% 86%


• Peas in stale seedbeds prepared 14 days prior to seeding were injured up to 70% by initial POST herbicides and flame (shallower seeding in firm seedbeds?)– Pea vine and pod weight was reduced the

most by glyphosate and paraquat

• Residual products provided 85 to 89% weed control, better than the 81% resulting when no residual product was used

• Green pea vine and pod fresh weight were not greatly affected by residual herbicide choice (about 2.8 kg/m2)

Weed Control At Pea Harvest

July, 2009

0

20

40

60

80

100

0 d 3 d 7 d 14 d


%94% 53% 96% 97%

Stale Seedbed Conclusions2007-09

• Weed control was generally good regardless of herbicide choice or flame– In 2007, flame and pyraflufen performed worse

than other herbicides, particularly with 14 d seedbed

– Ranged from 75 to 89% among all treatments in 2007-08 and from 80 to 99% in 2009

• Injury was 70% for 14 d seedbeds in 2009, and was worse with glyphosate and paraquat on those seedbeds in 2009

• Green pea did not respond greatly to seedbed timing any year– Weed control was slightly improved with 0 to 7 d

seedbeds compared to 14 d seedbeds

Spartan and Chateau Trial2003

• Two newer soybean herbicides with good nightshade activity and were tested for selectivity in pea – Spartan (sulfentrazone, FMC)– Chateau (flumioxazin, Valent)

• Tests conducted in Mount Vernon, Paterson (Rick Boydston), and Pullman (Joe Yenish) on green peas, dry peas, lentils, and chickpeas

Spartan and Chateau Trial

• Mount Vernon trial, 2003– ‘Snake’ pea seeded May 6– Herbicides applied alone and at 4 rates

each June 4, as well as in mixture with Prowl or Dual Magnum at 2 rates each

– Weed control and crop injury estimated– Peas and weeds harvested in late July

•Sampling within a 1-m2 quadrat•Pea yield calculated

Common Lambsquarters Counts Chateau

0

10

20

30

40

50Chat 0.6Chat 1Chat 1.5Chat 1.9Chat + Prowl lowChat + Prowl highChat + Dual lowChat + Dual high

weeds/m2

Counted 14 days after treatment

0

5

10

15

20

25

30Spart 1.3Spart 2Spart 2.7Spart 4Spart + Prowl lowSpart + Prowl highSpart + Dual lowSpart + Dual high

weeds/m2

Counted 14 days after treatment

Common Lambsquarters Counts Spartan

Mount Vernon Results• No significant

difference in weed control

• No significant difference in pea injury

• No significant difference in pea yield

Spartan and Chateau Trial

• Paterson trial, 2003– ‘Snake’ pea seeded April 21– Herbicides applied April 25 at same

rates and combinations as at Mount Vernon

– Weed control and crop injury estimated

– Peas and weeds harvested in late July•Sampling within a 1-m2 quadrat•Pea yield calculated

Pea Injury Chateau

0

10

20

30

40


%

Injury 35 days after treatment

Pea Yield Chateau

0

0.5

1

1.5

2

2.5


tons/a

Pea InjurySpartan

0

5

10

15

20

25


%

Injury 35 days after treatment

Pea YieldSpartan

0

0.5

1

1.5

2

2.5


tons/a

Spartan and ChateauConclusions

• Injury from tank mixtures of Chateau or Spartan with Dual Magnum or Prowl was excessive at Paterson

• Weed control from combination treatments was superior to that from Chateau or Spartan alone

• The manufacturers have deemed green pea too sensitive to these products for registration, so further testing was dropped

Many Thanks!• Funding for these studies provided by the

– Northwest Ag Research Foundation– WA State Commission on Pesticide

Registration– US Dry Pea and Lentil Council– Columbia Basin Vegetable Processors, – Pacific Northwest Vegetable Association

• Herbicides provided by the manufacturers• Pea seed from National Frozen Foods• Carl Libbey and the gang at WSU Mount

Vernon NWREC

weed control in green peas tim miller wsu mount vernon nwrec

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