Klamath Experiment Station
1995 Evaluation of the Herbicide Matrix on Russet Norkotah Potatoes at Klamath
Falls, Oregon K.A. Rykbost' and K.Locke 2
a.i./acre, was applied with a backpack sprayer
ntroduction
I
Preliminary evaluation has shown Matrix
(25 percent rimsulfuron evaluated as
E9636), alone or in combination with low
rates of Lexone, to be a promising alternative
to metribuzin products for post-emergence
broadleaf weed control in potato crops. This
is a particularly promising management tool
for varieties that are gaining importance in
western production areas, but are moderately
to highly sensitive to metribuzin injury. The
Shepody variety that has become dominant in
the Treasure Valley and important in the
Columbia Basin, is highly sensitive to
metribuzin injury. Atlantic and most redskinned varieties are also metribuzin-sensitive.
A study was conducted at the Klamath Experiment Station (KES) in 1995, to further evaluate Matrix for post-emergence weed control in
Russet Norkotah potatoes.
Procedures
Russet Norkotah potatoes were planted on
June 13 in a field cropped with spring barley in
1994. Seed was spaced at 9 inches in 32-inch
rows. Fertilizer was banded on both sides of
seed furrows at 730 lb/acre of 16-8-8-14 S.
Additional nitrogen fertilizer was applied at 30
lb N/acre as solution 32 with a conventional
ground sprayer on June 21. Individual plot
boundaries were established on June 22 to
accommodate 8 treatments of 4-row, 22-foot
plots with four replications. Eptam, at 3.0 lbs
11
to plots with treatment numbers 5-8 on June
22, and incorporated immediately by two
passes with a rolling cultivator.
Intended herbicide treatments included
Matrix at 0.0156, 0.0234, 0.0313 and 0.0468
lb ai/acre with a non-ionic surfactant at 0.25
percent by volume on four treatments at
ground cracking. Three treatments that
received Eptam were to be followed by Matrix
plus Lexone at two Lexone rates, or by
Lexone alone at 0.75 lb a.i./acre, applied at
layby. The fourth treatment with Eptam was
to serve as the control treatment.
Matrix was applied to treatments 1-4 with
a backpack sprayer on the morning of July 13.
Weather conditions at time of application were
calm and clear. Air temperature was approximately 55 °F at the time of application, with a
high of 72 °F and daily minimums of 35 and
48 °F on July 13 and 14, respectively. Soil
conditions were moist following precipitation
measured at 0.20 inches from mid-day rain on
July 12. Soil temperatures at the 4-inch depth
were 58 to 63 °F on July 13. All weather data
were recorded at the KES weather station
located approximately 1,000 feet from the trial
site.
Standard cultural practices were followed
for disease control. Total irrigation for the
season was about 16 inches, applied with
solid-set sprinklers at 40x48-foot spacing.
Weed control efficacy was rated on July 21.
Superintendent/Professor, Klamath Experiment Station, Klamath Falls, OR.
Klamath County Cooperative Extension Agent, Klamath Falls, OR.
Acknowledgments: Partial funding for the study from the Oregon Potato Commission and the E.I.
duPont de Nemours and Co., Inc., is gratefully recognized.
KLAMATH EXPERIMENT STATION 1995 129
Klamath Experiment Station
1995 Evaluation of the Herbicide Matrix on Russet Norkotah Potatoes at Klamath
Falls, Oregon
Percent of weeds present that appeared to be effectively controlled were recorded for
redroot pigweed and hairy nightshade on each
plot. Filaree and mallow control was scored
where these weeds were present. Vines were desiccated with Diquat applied at 0.25 lb ai/
acre on September 21.
Plants and tubers were removed, by hand,
from 2-foot borders between plots in the
center two rows on September 28. All re- maining tubers were harvested from the center two rows of each plot with a one-row, digger- bagger on October 4, and stored until grading was done on November 1. Tubers were graded to USDA standards, with separation of
U.S. No.ls into sizes of 4-12, and over 12
ounces. Yield and grade data were analyzed
statistically using MSUSTAT software.
Matrix was also used at approximately 0.0234 lb ai/acre on potatoes in another field
at KES in 1995. The field included over 5,000
single-hill, first generation red-skinned breed- ing selections, advanced red-skinned breeding
selections, several named red-skinned variet- ies, Shepody, and Russet Norkotah. Ad- vanced selections and Shepody were planted on June 20. Russet Norkotah and single-hill, red-skinned selections were planted on June 13. Eptam was applied to the entire field on June 21 at 3.0 lb ai/acre. Emergence was very erratic in the single-hill selections, which were planted using mini-tubers produced in green- house culture. Mini-tuber seed size ranged
from about 2 to 7 gms. These selections were
spaced 36 inches apart in 32-inch rows. Matrix was applied at 0.0234 lb ai/acre with 0.25 percent by volume R-11 surfactant
with a conventional ground sprayer on August
2. Weather conditions were clear skies, calm, and 75 °F. Potato plants ranged from just
130 KLAMATH EXPERIMENT STATION 1995
emerged to near row closure. Weeds ranged
from lambsquarter and redroot pigweed nearly
12 inches tall to nightshade and mallow plants
over 8 inches in diameter. Minor populations
of shepherds purse, filaree, Indian lovegrass,
and kochia were also present but plants were
quite small.
Results and Discussion
Planting was delayed until one month past
normal by wet soil conditions. Additional
rainfall of 1.04 inches was recorded at KES in
the 24 hours following planting of this trial.
These conditions led to some loss of stand due
to seed decay, and uneven emergence of plants.
The ground cracking timing varied by several
days. When Matrix was applied on July 13,
potato plants ranged from just emerging to
plants 4 inches high. Weed size varied from
cotyledon stage to 4-leaf stage or beyond.
Weed pressure was relatively light throughout
the study area.
Layby treatments were not applied as both
investigators were out of town during the
period these treatments should have been
made. As a result, treatment comparisons can
only be made between the four rates of Matrix
and an Eptam control. Efficacy ratings for
redroot pigweed, hairy nightshade, filaree, and
mallow are presented in Table 1. All Matrix
treatments provided complete control of these
species. Some pigweed and nightshade escapes were observed in each of the four Eptam
treatments. The data for Eptam control
represents an average for the four treatments
that received pre-emergence Eptam applications. No evidence of injury to potato foliage
was observed in any of the treatments.
Yield data, by grade, are presented in
Tables 2 and 3. Table 2 shows yields for all
Klamath Experiment Station
1995 Evaluation of the Herbicide Matrix on Russet Norkotah Potatoes at Klamath
Falls, Oregon
eight treatments, even though numbers 5-8
were identical. The statistical analysis presented in this table was done using all eight
treatments. In Table 3, statistical analysis only
included the four Matrix treatments and
treatment number 8.
The post-emergence application of Matrix
provided excellent control of the weed species
present at the trial site, while pre-emergence
application of 3.0 lb ai/acre of Eptam did not
give complete control of redroot pigweed or
hairy nightshade (Table 1). Yield and grade
data show a significantly higher yield of 4-12
ounce U.S. No.ls for the 2.0 and 3.0 ounce/
acre Matrix treatments than for all Eptam
treatments whether analyzed using all treatments or only one Eptam treatment. No
significant differences were found for any of
the other yield parameters, although Matrix at
2.0 ounces/acre produced numerically higher
total and total U.S. No.1 yields than all other
treatments. The data suggest application of
Eptam may produce some degree of crop
injury.
Weed control has been difficult to achieve
in the single-hill red-skinned selections in
previous years because of the inability to use
metribuzin products and the low plant density.
Significant hand weeding has been necessary in
these plots in each year since 1988. Matrix
provided very satisfactory weed control,
eliminating the need for hand weeding except
for a few of the largest pigweed and
lambsquarter plants. Most of the escapes were
stunted and deformed, and did not achieve 50
percent of normal size by mid-September.
Excellent control of nightshade and mallow
was observed. There was no evidence of
foliage injury to any of the many red-skinned
breeding selections or Shepody.
While circumstances did not allow evaluation of the combination of Matrix with Lexone,
this combination has been evaluated previously
at KES in trials with the Shepody variety.
Preliminary findings indicated that the product
was more effective in controlling nightshade
than metribuzin, and crop injury was minor,
except when application was made in a nearfrost situation.
The decision by E.I. du Pont de Nemours
and Co., Inc. to market the product, Matrix,
without adding Lexone, appears to be the
correct decision for the industry. The growing
acreage of metribuzin-sensitive varieties will
be best served by this product without adding
Lexone. Matrix will
be a very important
addition to the
arsenal of weapons
for weed control in
the northwest.
KLAMATH EXPERIMENT STATION 1995 131
Klamath Experiment Station
Table 1. Effect of herbicide treatments on four weed species in potatoes at the Klamath
Experiment Station, Klamath Falls, OR, 1995.
Treatment
No. Product Rate
Date
lb ai/A
Efficacy rating July 21
Pigweed Nightshade Filaree Mallow
% 1
7/13
3 Matrix00
0.0156
100
100
100
1 Matrix
0.0234
7/13
100
100
100
100
4 Matrx
0.0313
7/13
100
100
100
100
2 Matrix
0.0468
7/13
100
100
100
100
3.5
6/22
88
90
100
100
5 - 8 Eptam
132 KLAMATH EXPERIMENT STATION 1995
Klamath Experiment Station
Table 2. Effect of herbicide treatments on yield, grade, and size distribution of Russet Norkotah
potatoes at the Klamath Experiment Station, Klamath Falls, OR, 1995.
No.
Treatment
Product
Rate
Yield U.S. No. 1s
Total
4 - 12 oz
>12 oz
lb ai/A
Bs
No. 2s
Yield
Culls
Total
cwt/A
3
Matrix
0.0156
216
121
337
24
6
12
379
1
Matrix
0.0234
212
117
329
32
3
23
387
4
Matrix
0.0313
248
127
375
34
5
13
427
2
Matrix
0.0468
249
94
343
26
8
14
391
5
Eptam
3.5
189
135
324
26
7
17
374
6
Eptam
3.5
180
135
315
28
8
15
366
7
Eptam
3.5
211
99
310
28
2
12
352
8
Eptam
3.5
201
103
304
26
3
14
347
213
12
38
116
29
NS
330
13
NS
28
38
NS
5
91
NS
15
51
NS
378
12
NS
Mean
CV (%)
LSD (0.05)
KLAMATH EXPERIMENT STATION 1995 133
Klamath Experiment Station
Table 3. Effect of herbicide treatments on yield, grade, and size distribution of Russet Norkotah
potatoes at the Klamath Experiment Station, Klamath Falls, OR, 1995.
No.
Treatment
Rate
Product
Yield U.S. No. 1s
4 - 12 oz
>12 oz
Total
lb ai/A
Bs
Yield
No. 2s
Culls
Total
cwt/A
3
Matrix
0.0156
216
121
337
24
6
12
379
1
Matrix
0.0234
212
117
329
32
3
23
387
4
Matrix
0.0313
248
127
375
34
5
13
427
2
Matrix
0.0468
249
94
343
26
8
14
391
8
Eptam
3.5
201
103
304
26
3
14
347
225
11
36
112
27
NS
337
12
NS
29
38
NS
5
91
NS
15
51
NS
386
12
NS
Mean
CV (%)
LSD (0.05)
134 KLAMATH EXPERIMENT STATION 1995