Grass Weed Management During Establishment of Irrigated Grass Seed Crops
Daniel A. Ball
Oregon State University
Columbia Basin Ag. Research Center
Pendleton, OR
Introduction:
A trial was established under center pivot irrigation at a USDA-ARS research farm near
Paterson, WA, in autumn of 2009 to evaluate the influence of previous cropping history on rattail fescue (Vulpia
myrous) in Kentucky bluegrass (KBG) grown for seed. Rattail fescue is a winter annual grass weed that is a
critical problem in seedling KBG since no herbicide treatments have been identified to selectively control this
weed during establishment of KBG. Initial treatments included winter wheat seeded in autumn of 2009, or
green pea, potato, or sweet corn planted in spring of 2010. Production details for these crops are outlined in
Table 1. Following the production of these crops, a fine seedbed was prepared, and plot areas were split and
received either an application of metam-sodium1 or no treatment. The plot area was then conventionally
seeded to “Barduke” Kentucky bluegrass on August 30, 2010. Weed counts were obtained on September 7, 2010
to evaluate the effect of metam-sodium on early-season weed control (Table 2). This evaluation of weed
populations was done before emergence of the newly seeded KBG crop. The KBG planting was then followed by
a series of herbicide treatments (Tables 3,4a-4c). Preemergence (PRE) treatments were applied 7 September
2010, early postemergence (EPOST) treatments were applied 6 October, and late postemergence (LPOST)
treatments were applied 11 November, 2010. All postemergence (EPOST, LPOST) treatments included a crop oil
concentrate (COC) at 1% v/v and 32% N solution at 2.5% v/v. All herbicides were applied in 16 gal/A water.
Crop injury (Table 3) and weed control (Tables 4a-4c) were evaluated on 12 November, 2010.
1
Metam sodium applied 20 August 2010 at 20 gal/A rate as a broadcast spray in 29 gal/A water, and
immediately followed by overhead, pivot irrigation. Air and soil temperature at time of application 61F.
Table 1. Production details for crops grown prior to seedling Kentucky bluegrass. Paterson, WA 2010.
Crop
Variety
Preplant tillage
Seeding rate
Herbicide treatment
Seeding date
Harvest date
Additional note
Potato
Norkota
disked then furrowed
2400 lb/A
Outlook PRE 14 fl oz/A
Chateau PRE 1.5 oz/A
Sencor 75DF PRE 0.33 lb/A
9 April 2010
26 July 2010
--
Sweet corn
disked then harrowed
31,500 seeds/A
Outlook PRE 14 fl oz/A
Callisto PRE 6 fl oz/A
16 April 2010
5 August 2010
9 August flail chop
Winter wheat
WB 528 (SWW)
minimum tillage
90 lb/A
Bronate POST 1.5 pt/A
Sept 2009
9 August 2010
9 August flail chop
Green pea
Dakota
disked then harrowed
200 lb/A
MCPA POST 0.5 pt/A
+
Basagran POST 1 pt/A
24 Mar 2010
13 July
Table 2. Influence of previous crop and metam-sodium on preemergence weed counts to Kentucky
bluegrass.
Influence of previous crop and metam-sodium on
weed counts preemergence to Kentucky bluegrass
250
number of plants / m2
broadleaf weeds
200
other grasses
150
downy brome
rattail fescue
100
50
0
Pea w/
metam
sodium
Pea w/o
metam
sodium
Wheat w/
metam
sodium
Wheat w/o
metam
sodium
Corn w/
metam
sodium
Corn w/o
metam
sodium
Potato w/
metam
sodium
Potato w/o
metam
sodium
Table 3. Kentucky bluegrass crop injury from herbicide treatments. Evaluated on November 12, 2010.
Paterson, WA 2010.
Trt Herbicide
1
2
3
4
5
6
7
8
Rate (oz/A)
Timing1
No herbicide
--Callisto / Callisto
3/3
PRE/EPOST
Callisto / Callisto+Beacon 3 / 3+0.187 PRE/EPOST
Callisto+Beacon
6+0.187
EPOST
Callisto / Callisto+Beacon 3 / 3+0.187 EPOST/LPOST
Callisto+Beacon / Callisto 3+0.187 / 3 EPOST/LPOST
Callisto+Beacon
3+0.187
LPOST
Callisto+Everest
3+0.6
LPOST
LSD (0.05) for fumigant
LSD (0.05) for herbicide
No fumigation
Metam-sodium
KBG crop injury
---------------- % visible injury ---------------0
0
0
0
18
12
12
12
0
0
10
15
--3
--3
--3
--3
ns
4
1
Metam-sodium applied on 20 August 2009 @ 20 ga/A with a broadcast boom sprayer and immediately
incorporated to a 2-3 inch depth with a power tiller.
2
Evaluations of potato ground, only.
3
Evaluations made only 1 day after LPOST treatments, so these values not reported.
Results and Discussion:
Metam-sodium applied at 20 gal/A had an observable effect on reducing early-
season grass weeds including rattail fescue (Tables 2, 4a-c), but not at a statistically significant level. By itself,
metam-sodium provided early suppression of rattail fescue, but did not provide sufficient residual weed control.
Broadleaf weed control from metam-sodium was evident, early season, but was negligible by mid-season.
Treatments containing an EPOST application of Beacon caused injury to KBG (Table 3) including stunting which
was evident for a considerable amount of time during the growing season. Herbicide treatments with Callisto
provided nearly complete control of broadleaf weeds (Tables 4a-c) and several summer annual grasses such as
lovegrass (data not shown); with no apparent KBG crop injury (Table 3). Callisto treatments applied PRE or
EPOST were equally effective in controlling broadleaf weeds (Tables 4a-c). Callisto did not appear to reduce
rattail fescue density. In addition to causing KBG crop injury (Table 3), Beacon at the low rate tested (0.187
oz/A) resulted in no additional weed control benefit compared to Callisto, alone.
KBG was swathed on 24 June, 2011 and harvested with a small-plot combine on 30, June. Due to difficulties
with combine settings and operation, and due to a considerable amount of weed contaminants, clean seed yield
was noticeably reduced and highly variable. Variability in obtained clean seed yield resulted in no statistically
significant differences between the fumigated and non-fumigated plots (data not shown), although there were
visible differences in weed control throughout the growing season. Similarly, the high degree of variability in
clean seed yields prevented elucidation of weed control impacts (Table 5). However, there was a trend for
reduced KBG seed yield in treatments that included EPOST Beacon, even at the greatly reduced rate applied in
this trial.
By far, the largest impact on rattail fescue populations was the result of previous cropping (see attached
photos). The KBG planting following winter wheat was a complete loss due to overwhelming densities of rattail
fescue and downy brome (see attached photos). KBG plantings following spring pea, sweet corn, or potatoes
were completely successful with negligible to slight levels of rattail fescue and downy brome. The preplant
metam-sodium fumigation followed by Callisto treatment provided nearly complete control of all weeds
encountered in this trial (Tables 4a-c).
Acknowledgements:
Funding for this trial was granted through the USDA-CSREES Grass Seed Cropping
Systems for a Sustainable Agriculture (GSCSSA) Special Grant, and from the Washington State Turfgrass Seed
Commission. Logistical and technical support from Rick Boydston and Marc Seymour, USDA-ARS, Prosser, WA is
also acknowledged and greatly appreciated.
Table 4a. Weed control in Kentucky bluegrass following potato. Paterson, WA 2010.
Trt
Herbicide
Rate (oz/A)
1
2
3
4
5
6
7
8
No herbicide
Callisto / Callisto
Callisto / Callisto+Beacon
Callisto+Beacon
Callisto / Callisto+Beacon
Callisto+Beacon / Callisto
Callisto+Beacon
Callisto+Everest
LSD (0.05) for fumigant
LSD (0.05) for herbicide
-3/3
3 / 3+0.187
6+0.187
3 / 3+0.187
3+0.187 / 3
3+0.187
3+0.6
Timing1
No
MetamNo
MetamNo
Metamfumigation
sodium
fumigation
sodium
fumigation
sodium
Rattail fescue
Downy brome
Broadleaf weeds
-------------------------------------- plants / m2 ----------------------------------------------4
1
0
0
12
13
PRE/EPOST
4
0
0
0
0
0
PRE/EPOST
5
0
0
0
0
0
EPOST
3
0
0
0
0
0
EPOST/LPOST
7
0
0
0
0
0
EPOST/LPOST
7
0
0
0
0
3
2
2
2
2
2
LPOST
3
0
0
0
12
192
LPOST
32
02
02
02
162
142
3
ns
ns
ns
ns
7
Table 4b. Weed control in Kentucky bluegrass following sweet corn. Paterson, WA 2010.
Trt
Herbicide
Rate (oz/A)
1
2
3
4
5
6
7
8
No herbicide
Callisto / Callisto
Callisto / Callisto+Beacon
Callisto+Beacon
Callisto / Callisto+Beacon
Callisto+Beacon / Callisto
Callisto+Beacon
Callisto+Everest
LSD (0.05) for fumigant
LSD (0.05) for herbicide
-3/3
3 / 3+0.187
6+0.187
3 / 3+0.187
3+0.187 / 3
3+0.187
3+0.6
Timing1
No
MetamNo
MetamNo
Metamfumigation
sodium
fumigation
sodium
fumigation
sodium
Rattail fescue
Downy brome
Broadleaf weeds
-------------------------------------- plants / m2 ----------------------------------------------9
1
0
0
21
24
PRE/EPOST
3
0
0
0
1
0
PRE/EPOST
7
0
0
0
1
0
EPOST
2
0
0
1
1
0
EPOST/LPOST
9
2
0
1
0
1
EPOST/LPOST
5
0
0
0
1
0
LPOST
52
22
02
02
232
242
LPOST
32
12
12
02
302
232
ns
ns
ns
ns
ns
5
1
PRE treatments applied 7 September 2010, EPOST applied 6 October, and LPOST applied 11 November, 2010. Weed control evaluated on 12
November, 2010. Postemergence (EPOST, LPOST) treatments included a crop oil concentrate (COC) at 1% v/v and 32% N solution at 2.5% v/v.
2
Evaluations made only 1 day after LPOST treatments, so these values do not reflect expected final weed control.
Table 4c. Weed control in Kentucky bluegrass following green processing pea. Paterson, WA 2010.
Trt
Herbicide
Rate (oz/A)
1
2
3
4
5
6
7
8
No herbicide
Callisto / Callisto
Callisto / Callisto+Beacon
Callisto+Beacon
Callisto / Callisto+Beacon
Callisto+Beacon / Callisto
Callisto+Beacon
Callisto+Everest
LSD (0.05) for fumigant
LSD (0.05) for herbicide
-3/3
3 / 3+0.187
6+0.187
3 / 3+0.187
3+0.187 / 3
3+0.187
3+0.6
Timing1
No
MetamNo
MetamNo
Metamfumigation
sodium
fumigation
sodium
fumigation
sodium
Rattail fescue
Downy brome
Broadleaf weeds
--------------------------------------- plants / m2 ---------------------------------------------7
6
1
0
19
24
PRE/EPOST
9
2
1
0
0
0
PRE/EPOST
5
3
1
1
0
6
EPOST
7
2
2
1
0
1
EPOST/LPOST
2
5
5
0
1
1
EPOST/LPOST
4
4
2
1
1
1
2
2
2
2
2
LPOST
5
3
1
0
13
172
LPOST
72
32
32
12
142
152
ns
ns
ns
ns
ns
10
1
PRE treatments applied 7 September 2010, EPOST applied 6 October, and LPOST applied 11 November, 2010. Weed control evaluated on 12
November, 2010. Postemergence (EPOST, LPOST) treatments included a crop oil concentrate (COC) at 1% v/v and 32% N solution at 2.5% v/v.
2
Evaluations made only 1 day after LPOST treatments, so values do not reflect expected final weed control.
Table 5. Kentucky bluegrass clean seed yield averaged across all rotational crops. Paterson, WA 2011.
Trt Herbicide
1
2
3
4
5
6
7
8
Rate (oz/A)
Timing1
No herbicide
--Callisto / Callisto
3/3
PRE/EPOST
Callisto / Callisto+Beacon 3 / 3+0.187 PRE/EPOST
Callisto+Beacon
6+0.187
EPOST
Callisto / Callisto+Beacon 3 / 3+0.187 EPOST/LPOST
Callisto+Beacon / Callisto 3+0.187 / 3 EPOST/LPOST
Callisto+Beacon
3+0.187
LPOST
Callisto+Everest
3+0.6
LPOST
No fumigation
342
288
201
283
299
239
296
323
Metam-sodium
Average
KBG clean seed yield
---------------- lb/A ---------------314
328
298
293
286
243
188
235
298
299
169
204
294
295
224
273