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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
Reduced Rate Herbicide Trials
• Tested herbicides were:– Command, PRE– Sencor, PRE and POST– Basagran, POST– MCPA, POST
• Various combinations of these products were tested at various rates
Reduced Rate Herbicide Trials
• 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)
Reduced Rate Herbicide Trials
• 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)
Reduced Rate Herbicide Trials
• 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
Reduced Rate Herbicide Trials
• 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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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)
Com + Sen (PRE,POST)Untreated
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
Stale Seedbed Trial Overview
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
Stale Seedbed Trial Overview
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
Stale Seedbed Trial Overview
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%
Stale Seedbed Trial2008 Results
• 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
GlyphosateParaquatGlufosinatePyraflufenFlameCheck
%
86% 79% 83% 86%
Stale Seedbed Trial2009 Results
• 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
GlyphosateParaquatGlufosinatePyraflufenFlameCheck
%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
50Chat 0.6Chat 1Chat 1.5Chat 1.9Chat + Prowl lowChat + Prowl highChat + Dual lowChat + Dual high
%
Injury 35 days after treatment
Pea Yield Chateau
0
0.5
1
1.5
2
2.5
3Chat 0.6Chat 1Chat 1.5Chat 1.9Chat + Prowl lowChat + Prowl highChat + Dual lowChat + Dual high
tons/a
Pea InjurySpartan
0
5
10
15
20
25
30Spart 1.3Spart 2Spart 2.7Spart 4Spart + Prowl lowSpart + Prowl highSpart + Dual lowSpart + Dual high
%
Injury 35 days after treatment
Pea YieldSpartan
0
0.5
1
1.5
2
2.5
3Spart 1.3Spart 2Spart 2.7Spart 4Spart + Prowl lowSpart + Prowl highSpart + Dual lowSpart + Dual high
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