Weed Control in
Green Peas
Tim Miller
WSU 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 weedfree until harvest
– 1, 2, 3, 4, 5, and 6 weeks after
emergence
• Weedy and weed-free plots
Pea Density and Pea Weight
2001-03
350
300
Weed free
1 week
2 weeks
3 weeks
4 weeks
5 weeks
6 weeks
Full
250
200
150
100
50
0
plants/plot
100 pea wt. (g)
Pod Production and Pea Yield
2001-03
8
Weed free
1 week
2 weeks
3 weeks
4 weeks
5 weeks
6 weeks
Full
6.4
4.8
3.2
1.6
0
pods/plant
yield (tons/a)
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 Yield
2001-03
tons/a
Com + Bas
4.8
Sen (Hi, PRE)
3.2
a
ab
1.6
0
ab
ab
Com (Hi)
a
Com + Sen (PRE)
g
Com + Sen (PRE,
POST)
Untreated
Biomass Returned to the Field
2001-03
tons/a
Com + Bas
4.8
abc
3.2
ab abc a ab
1.6
Command (Hi)
bcd
hij ghi
g
ij ij
j
0
Sencor (Hi, PRE)
Pea dry weight
Weed dry weight
Com + Sen (PRE)
Com + Sen (PRE,
POST)
Untreated
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 Ratio
2001-03
Com + Bas
20
15
a
Sencor (Hi, PRE)
Command (Hi)
10
5
0
Com + Sen (PRE)
b
bc
cd
d
d
Com + Sen (PRE,
POST)
Untreated
weeds/m2
Common Lambsquarters
Germination Counts
2002 only
Com + Bas
2000
Sen (Hi, PRE)
1500
Com (Hi)
1000
Com + Sen (PRE)
500
0
Fall
Spring
Total
Com + Sen (PRE,
POST)
Untreated
Pineappleweed Germination Counts
2002 only
2
weeds/m
Com + Bas
1000
800
Sen (Hi, PRE)
600
Com (Hi)
400
Com + Sen (PRE)
200
Com + Sen (PRE,
POST)
Untreated
0
Fall
Spring
Total
Shepherd’s-purse Germination Counts
2002
only
2
weeds/m
600
Com + Bas
500
Sen (Hi, PRE)
400
Com (Hi)
300
Com + Sen (PRE)
200
100
0
Fall
Spring
Total
Com + Sen (PRE,
POST)
Untreated
Reduced Rate Herbicide Trial—Total
Weed Seed Germination Counts
weeds/m2
10000
Com + Bas
8000
Sen (Hi, PRE)
6000
Com (Hi)
4000
Com + Sen (PRE)
2000
Com + Sen (PRE,
POST)
Untreated
0
Fall
Spring
Total
Reduced Rate Herbicide Trial—Total
Weed Seed Germination Counts
weeds/m2
10000
Com + Bas
8000
Sen (Hi, PRE)
6000
Com (Hi)
4000
Com + Sen (PRE)
2000
Com + Sen (PRE,
POST)
Untreated
0
Fall
Spring
Total
Reduced Rate Herbicide Trial—Total
Weed Seed Germination Counts
weeds/m2
10000
Com + Bas
8000
Sen (Hi, PRE)
6000
Com (Hi)
4000
Com + Sen (PRE)
2000
Com + Sen (PRE,
POST)
Untreated
0
Fall
Spring
Total
Weed Seed Germination
• 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)
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 Seedbed
Allow 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 Trial
2007 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 Harvest
July, 2007
%
100
80%
83%
78%
67%
80
Glyphosate
Paraquat
Glufosinate
Pyraflufen
Flame
Check
60
40
20
0
0d
3d
7d
14 d
Stale Seedbed Trial
2008 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
%
100
86%
83%
86%
79%
80
Glyphosate
Paraquat
Glufosinate
Pyraflufen
Flame
Check
60
40
20
0
0d
3d
7d
14 d
Stale Seedbed Trial
2009 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
%
97%
96%
94%
53%
100
80
Glyphosate
Paraquat
Glufosinate
Pyraflufen
Flame
Check
60
40
20
0
0d
3d
7d
14 d
Stale Seedbed Conclusions
2007-09
• 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 Trial
2003
• 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
weeds/m2
Chateau
50
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40
30
20
10
0
Counted 14 days after treatment
0.6
1
1.5
1.9
+ Prowl low
+ Prowl high
+ Dual low
+ Dual high
Common Lambsquarters Counts
weeds/m2
Spartan
30
Spart
Spart
Spart
Spart
Spart
Spart
Spart
Spart
25
20
15
10
5
0
Counted 14 days after treatment
1.3
2
2.7
4
+ Prowl low
+ Prowl high
+ Dual low
+ Dual high
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
50
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40
30
20
10
0
Injury 35 days after treatment
0.6
1
1.5
1.9
+ Prowl low
+ Prowl high
+ Dual low
+ Dual high
Pea Yield
tons/a
Chateau
3
2.5
2
1.5
1
0.5
0
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0.6
1
1.5
1.9
+ Prowl low
+ Prowl high
+ Dual low
+ Dual high
Pea Injury
%
Spartan
30
Spart
Spart
Spart
Spart
Spart
Spart
Spart
Spart
25
20
15
10
5
0
Injury 35 days after treatment
1.3
2
2.7
4
+ Prowl low
+ Prowl high
+ Dual low
+ Dual high
Pea Yield
tons/a
Spartan
3
2.5
2
1.5
1
0.5
0
Spart
Spart
Spart
Spart
Spart
Spart
Spart
Spart
1.3
2
2.7
4
+ Prowl low
+ Prowl high
+ Dual low
+ Dual high
Spartan and Chateau
Conclusions
• 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