Tank mix combinations with Roundup̉ for weed control in Roundup-Readỷ sugar beet

Don W. Morishita and Michael J. Wille

 

INTRODUCTION

Currently, sugar beet growers typically make three or more postemergence herbicide applications for weed control. Studies were conducted at the University of Idaho Research and Extension Center near Kimberly in 1998 and 1999 to evaluate Roundup̉ tank mixtures with soil-active herbicides applied postemergence for weed control in Roundup-Readỷ sugar beets.

MATERIALS AND METHODS

Sugar beets (‘Pillar RR’) were planted April 15, 1999, on 22-inch rows at a seeding rate of 47,520 seed/A and grown under sprinkler irrigation. Soil type was a Portneuf silt loam with a pH of 7.9, 1.45% organic matter, and CEC of 17.5 meq/100 g soil. The experimental design was a randomized complete block with four replications. Individual plots were 4 rows by 30 ft. All herbicides were applied with a CO2-pressurized bicycle-wheel sprayer calibrated to deliver 10 gpa using 11001 flat fan nozzles spaced 16 inches apart. Additional application information and weed species densities are shown in Table 1. Weed control was evaluated visually July 12, 21 days after last treatment (DAT). Sugar beet roots were harvested September 22 with a mechanical harvester.

Table 1. Application data and weed species densities.

Application date

5/24

6/7

6/24

Air temperature (F)

80

70

74

Soil temperature (F)

80

80

63

Relative humidity (%)

68

46

50

Wind speed (mph)

5

5

4

Cloud cover (%)

50

20

30

Weed species/ft2

Common lambsquarters

9

9

-

Kochia

6

5

-

Volunteer wheata

-

-

-
aNo density counts were taken.

 

RESULTS AND DISCUSSION

None of the herbicide treatments injured the crop (Table 2). All single applications of Roundup applied in combination with Nortron, Frontier X2, or Dual II Magnum controlled common lambsquarters, kochia, and volunteer wheat 93 to 100%. These treatments were as effective controlling weeds in this study as the sequential Roundup applications. All herbicide treatments had root and extractable sugar yields greater than the check. There were no differences among herbicide treatments in root yield. However, Roundup applied three times beginning at the 1 to 2 lf stage had a higher extractable sugar yield than three of the Roundup tank mixtures with soil-applied herbicides. Based on data from 1998 and 1999, it appears that weeds in sugar beet can be controlled with a single Roundup plus soil-applied herbicide tank mix application.

Table 2. Effect of Roundup tank mix combinations on crop injury, weed control, and yield in Roundup resistant sugar beet.

Weed Controla
Crop injury Colq Kochia Wheat

Treatment

 Rateb Application timing 7/12 7/12 7/12 7/12 Yield Extractable sugar

oz/A

-----------------%-----------------

 ton/A lb/A

Check

 - - - - 7 2400

Roundup+
Nortron

 16+
32

 4-6 leaf 0 97 96 96 19 5700

Roundup+ FrontierX2

 16+
14

 4-6 leaf 0 96 97 97 15 4900

Roundup+ FrontierX2

 16+
27

 4-6 leaf 0 100 99 99 23 7100

Roundup+
Dual II Magnum

 16+
22

 4-6 leaf 0 95 93 93 19 5700

Roundup+
Dual II Magnum

 16+
44

 4-6 leaf 0 98 100 100 25 7400

Roundup+
Dual II Magnum/
Roundup

 16+
27/
16 		1-2 leaf

4-6 leaf

 0 96 97 97 25 7300

Roundup/
Roundup+
Dual II Magnum

 16/
16+
27 		1-2 leaf

4-6 leaf

 0 96 97 93 25 7900

Roundup/
Roundup/
Roundup+
Dual II Magnum

 16/
16/ 
16+ 
27

 1-2 leaf
4-6 leaf

8-10 leaf

 0 100 100 100 23 6900

Roundup/
Roundup/
Roundup

 16/
16/
16

 1-2 leaf
4-6 leaf 
8-10 leaf

 0 100 100 100 26 8100

LSD (0.05)

 ns ns ns ns 7 2200

aWeed species evaluated were common lambsquarters (Colq), kochia, and volunteer wheat (wheat).

bRate of application based on a broadcast basis. Amount applied in a band will vary depending in band width.

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