Klamath Experiment Station
Weed Control in Sugarbeets
K. Locke', R.L. Dove1 2 , and K.A. Rykbost 2
I
ntroduction
Lack of adequate weed control continues
to be the most limiting factor for profitable sugarbeet production in the intermountain region. The cost of chemical and
mechanical weed control represents 20 percent
of variable costs of production. Field trials
were conducted to evaluate herbicides for
sugarbeet tolerance and weed control.
Procedures
The study site was previously planted to
potatoes. Field cultural practices are described
on page 77. The variety WS 62 was planted in
22-inch rows on May 17, and hand-thinned to
approximately 30,000 plants/acre on June 27.
The study consisted of three-row plots, 25 feet
long, with seven treatments replicated five
times. Chemical treatments were applied with
a CO 2 backpack sprayer in 20 gallons per acre
(gpa) of solution on May 31, June 9, and June
13. Weed species were identified and counted
from a 15-square-foot quadrant of the middle
row on August 10. Plots were allowed to go
to harvest without further weed control. Beets
were hand harvested on October 16. Yields
were measured from the center row. An
approximate 30 pound sample from each plot
was collected and analyzed for tare loss and
sugar content.
Results and Discussion
The first treatments were applied when the
sugarbeets and weeds were in the cotyledon
stage. Redroot pigweed, hairy nightshade, and
lambsquarter were the main weed species.
Redstem filaree, mallow, and volunteer potatoes were present in minor numbers. Treatments are defined in Table 1. All treatments
gave significantly better weed control than the
check (Figure 1). Herbicide treatments were
not significantly different in weed control from
each other. Slight early phytotoxicity symptoms noted in treatment 5, the three-way
combination, were not reflected in the yield
data (Table 2). Treatment 5 controlled weeds
better than the other treatments (Figure 1), but
it was not more cost effective than treatment 6
due to a slight reduction in sugar produced
(Table 2).
Yields for the control treatment would be
less than reported if the crop had been harvested with commercial equipment. Most of
the beets in control plots were under 2 inches
in diameter. Although they were recovered in
hand harvesting, many would have been lost in
a mechanized harvest.
The combination treatments with Upbeet,
Stinger, and Nortron SC would not justify the
extra expense and added work, at least on the
weed spectrum in this study. Betamix
/ Klamath County Cooperative Extension Agent, Klamath Falls, OR.
21 Associate Professor and Superintendent/Professor, respectively, Klamath Experiment Station,
Klamath Falls, OR.
1
Acknowledgments: Financial support for the study, provided by the California Beet Growers Association and E.I. du Pont de Nemours and Co., Inc., and sample analyses provided by Spreckels Sugar
Company, are gratefully recognized.
KLAMATH EXPERIMENT STATION 1995 89
Klamath Experiment Station
Weed Control in Sugarbeets
Progress alone continues to be the most cost
effective treatment in this study. The gross
value column in Table 2 was calculated using
an average value of $44.92/ton.
90 KLAMATH EXPERIMENT STATION 1995
Klamath Experiment Station
Table 1. Herbicide treatments evaluated for sugarbeets at Klamath Falls, OR, 1995.
Treatment
number Product and rate
Application
date(s)
1
Untreated Control
2
Betamix @ 0.25 lb ai/A
Betamix @ 0.33 lb ai/A
5/31
6/9 & 6/13
3
Betamix @ 0.25 lb ai/A + Upbeet @ 0.5 oz/A
Betamix @ 0.33 lb ai/A + Upbeet @ 0.5 oz/A
5/31 & 6/9
6/13
4
Upbeet @ 0.5 oz/A + Stinger @ 3 fl. oz/A
+ Surfactant @ 1/4 % v/v
5/31 & 6/9
Upbeet @ 0.5 oz/A + Stinger @ 3 fl. oz/A
+ Nortron SC @ 8 fl. oz /A + Surfactant @ 1/4 % v/v
5/31 & 6/9
6
Betamix Progress @ 0.25 lb ai/A
Betamix Progress @ 0.33 lb ai/A
5/31
6/9 & 6/13
7
Betamix Progress @ 0.25 lb ai/A + Upbeet @ 0.5 oz/A Betamix Progress @ 0.33 lb ai/A + Upbeet @ 0.5 oz/A 5/31
6/9 & 6/13
5
KLAMATH EXPERIMENT STATION 1995
91
Klamath Experiment Station
Figure 1. Effect of herbicide treatments on density of lambsquarter (LQ), hairy
nightshade (NS), redroot pigweed (RP), and the three-species total in sugarbeets grown
at Klamath Falls, OR, 1995.
•
U)
60
40
'CT) 20
-0
a)
Total
t.1)0
12 3 4RP
NS
5 6 7
LQ
Treatments
92 KLAMATH EXPERIMENT STATION 1995
Klamath Experiment Station
Table 2. Effect of seven herbicide treatments on beet yield, sugar content,
sugar production, and gross value of sugarbeets grown at
Klamath Falls, OR, 1995.
Treatment/rate
Beet
Sugar
Sugar
Gross
yield
content
production
value
ton/A
`)/0
ton/A
$/A
1. Control
7.7
17.5
1.35
324
2. Betamix
20.2
17.5
3.52
851
3. Betamix + Upbeet
20.2
17.3
3.49
842
4. Upbeet + Stinger
21.4
17.6
3.72
906
5. Upbeet + Stinger + Nortron
21.1
17.7
3.75
898
6. Betamix Progress
22.1
17.5
3.85
931
7. Betamix Progress + Upbeet
21.4
17.5
3.74
902
Mean
CV(%)
LSD (0.05)
19.2
6
3.2
17.5
2
1.2
3.30
5
0.51
808
5
125
KLAMATH EXPERIMENT STATION 1995 93