Malheur Experiment Station
Oregon State University
Information for Sustainable Agriculture

DEVELOPMENT OF NEW HERBICIDE OPTIONS FOR WEED CONTROL IN POTATO PRODUCTION

Corey V. Ransom, Charles A. Rice, and Joey K. Ishida
Malheur Experiment Station
Oregon State University
Ontario, OR, 2003

Introduction

Weed control in potatoes is essential for production of high yielding, marketable tubers. Herbicide options in potato production are limited. Outlook (dimethenamid-P), Spartan (sulfentrazone), and Chateau (flumioxazin) are new herbicides that have demonstrated great promise for use in potato. Spartan and Chateau (reported as Valor in previous reports) represent a mode of action that is not currently used in potatoes and offer excellent hairy nightshade control. In previous weed control trials at the Malheur Experiment Station, Outlook (dimethenamid-P) has controlled a larger spectrum of weeds than several other herbicides registered in potato. Trials were conducted to evaluate these new herbicides for weed control in potatoes. The results of our research have been provided to herbicide companies, the IR4 program, and state regulators in support of additional herbicide registrations in potatoes. Spartan has been registered for use in potato this year and a full label for Outlook is expected for 2005. The registration of these herbicides gives producers additional tools to use for controlling weeds and may increase economic returns through improved weed control.

Materials and Methods

A field trial was conducted at the Malheur Experiment Station to evaluate new herbicides for weed control efficacy and crop tolerance in potatoes. In the fall of 2002, 100 lbs P, 150 lbs K, 40 lbs elemental S, 6 lbs Mn, 2 lbs Zn, 2 lbs Cu, and 1 lb B/acre were applied to the trial area prior to bedding. Potatoes were planted April 24, 2003 in an Owyhee silt loam soil with pH 7.6, 2.1 percent organic matter content, and a cation exchange capacity of 20. 'Russet Burbank' seed pieces were planted every 9 inches in 36-inch-wide rows. Experimental plots were four rows wide and 30 ft long. Plots were sidedressed with 100 lb N/acre on May 13 and rehilled on May 19. Preemergence herbicide treatments were applied and immediately incorporated with 0.5 inch of sprinkler-applied irrigation water on May 19. Herbicides were applied with a CO2-pressurized backpack sprayer delivering 20 gal/acre at 30 psi. On June 23, 20 lb N/acre was applied through the sprinkler. On August 8, 10 lb/acre of 'HighPhos PKS' (10-45-10) including 3 percent S, 0.02 percent B, 0.05 percent Cu, 0.1 percent Fe, 0.05 percent Mn, 0.0005 percent Mo, and 0.05 percent Zn was applied by airplane. Disease and insect management were accomplished by appliying Ridomil Gold plus Bravo (2 lb/acre) on June 19, sulfur dust (40 lb/acre) on July 20, and Bravo (1.5 pt/acre) plus Sulpreme (1 gal/acre) on August 4. Potato injury and weed control were evaluated throughout the growing season and tuber yields were determined by harvesting the center two rows of each plot on September 9-11. Potatoes were graded for yield and size on September 12-17.

Results and Discussion

Many herbicides provided excellent weed control in this trial (Table 1). Sencor (metribuzin) alone provided greater than 95 percent control of all weed species. Control of pigweed species was the lowest with Prowl (pendimethalin) and was less than 70 percent with Dual Magnum (s-metolachlor), Eptam (EPTC), and Chateau alone. Dual Magnum plus Prowl also had less pigweed control than other tank mixtures. On August 25, common lambsquarters control was lowest with Dual Magnum. Prowl and Chateau alone provided only 59 and 52 percent control of common lambsquarters while other treatments provided 68-100 percent control. Matrix (rimsulfuron) alone provided the least hairy nightshade control. Control with all other herbicides applied alone provided 90-100 percent hairy nightshade control. Chateau provided little barnyardgrass control unless tank mixed with another herbicide. Spartan gave greater than 94 percent control of all broadleaf weeds and 89 percent control of barnyardgrass. Chateau caused up to 21 percent injury 22 days after treatment, but no treatments had any injury 35 days after treatment (data not shown). In general, yields reflected weed control; treatments with poor weed control also had reduced potato yields (Table 2). There were cases where treatments providing similar weed control had significantly different yields. Spartan plus Prowl and Spartan plus Dual Magnum provided nearly identical levels of weed control, but Spartan plus Prowl had significantly higher tuber yields. These differences could not be explained by crop injury since no differences in potato injury between these treatments were observed during the season.

Table 1. Outlook, Spartan, and Chateau combinations for weed control in potato, Malheur Experiment Station, Oregon State University, Ontario, OR, 2003.
Weed control Weed control Weed control Weed control Weed control Weed control Weed control Weed control


Pigweed spp.†
 Pigweed spp.† Common lambsquarters Common lambsquarters Hairy nightshade
 Hairy nightshade Kochia
 Kochia Barnyard grass
Treatment*       
Rate 6-23
 8-25
 6-23
 8-25
 6-23
 8-25
 6-23
 8-25
 8-25

lb-ai/acre
% % % % % % % % %
Untreated control
 --
 -
 -
 -
 -
 -
 -
 -
 -
 -
Handweeded --
 -
 -
 -
 -
 -
 -
 -
 -
 -
Sencor
 0.5
 99
 98
 100
 100
 100
 95
 100
 100
 96
Prowl
 1.0
 69
 40
 84
 59
 100
 90
 100
 93
 74
Dual Magnum
 1.34
 84
 66
 73
 21
 97
 96
 83
 59
 95
Eptam
 3.0
 89
 68
 86
 84
 98
 94
 96
 79
 98
Spartan
 0.141
 100
 95
 98
 94
 100
 100
 100
 100
 89
Chateau
 0.094
 94
 68
 97
 52
 100
 93
 100
 94
 31
Outlook
 0.656
 96
 90
 94
 73
 99
 90
 99
 95
 98
Matrix
 0.023
 97
 88
 92
 68
 94
 76
 98
 93
 69
Spartan+Sencor
 0.141+0.5
 100
 100
 97
 100
 100
 100
 100
 100
 100
Spartan + Prowl 0.141+1.0
 100
 98 100 100 100 100 100 100 100
Spartan+DualMagnum 0.141+1.34
 100
 98
 100
 100
 100
 100
 100
 100
 98
Spartan + Eptam
 0.141 + 3.0 100
 98
 100
 99
 100
 100 100 100 100
Spartan + Matrix
 0.141+0.023
 100
 98
 100
 97
 100
 100
 100
 100
 91
Chateau + Sencor
 0.094 + 0.5
 100
 100
 100
 100
 100
 100
 100
 100
 97
Chateau + Prowl
 0.094 + 1.0
 100
 88
 99
 79
 100
 100
 100
 97
 61
Chateau+DualMagnum 0.094 + 1.34 100
 100
 98
 93
 100
 100
 100
 99
 76
Chateau + Eptam
 0.094 + 3.0
 100
 100
 100
 97
 100
 100
 100
 100
 100
Chateau + Matrix
 0.094+0.023
 100
 98
 100
 90
 100
 98
 100
 100
 98
Outlook + Sencor
 0.656 + 0.5
 100
 98
 100
 98
 100
 100
 100
 100
 100
Outlook + Matrix
 0.656+0.023
 100
 99
 99
 95
 100
 100
 100
 100
 100
Spartan + Outlook
 0.141+0.656
 100
 100
 100
 98
 100
 100
 100
 100
 100
Chateau + Outlook
 0.094+0.656
 100
 96
 100
 97
 100
 100
 100
 100
 93
Prowl + Matrix
 1.0 + 0.023
 100
 92
 100
 92
 98
 81
 100
 100
 92
Outlook + Prowl
 0.656 + 1.0
 96
 95
 100
 97
 100
 100
 100
 98
 98
Dual Magnum + Prowl
 1.34 + 1.0
 92
 76
 99
 86
 100
 94
 100
 98
 97
Dual Magnum+Sencor 1.34 + 0.5
 100
 100
 100
 98
 100
 100
 100
 100
 99
Dual Magnum+Matrix
 1.34 + 0.023 100
 98
 97
 83
 98
 100
 100
 100
 100
Prowl + Eptam
 1.0 + 3.0
 100
 91
 100
 100
 100
 100
 98
 98
 98
LSD (0.05)
7
 17
 7
 17
 3
 13
 5
 13
 24
*Herbicide treatments were applied preemergence on May 19. Chateau was reported as Valor in previous reports.
†Pigweed species were a combination of Powell amaranth and redroot pigweed.

Table 2. Outlook, Spartan, and Chateau combinations for weed control in potato, Malheur Experiment Station, Oregon State University, Ontario, OR, 2003.
Potato yield† Potato yield† Potato yield† Potato yield† Potato yield† Potato yield† Potato yield† Potato yield†


U.S. No.1
 U.S. No. 1 U.S. No. 1 U.S. No. 1 U.S. No.1


Treatment*
 Rate        
4-6 oz
 6-12 oz
 >12 oz
 Total
 Percent Total No.2 Total marketable Total yield

lb ai/acre cwt/acre
cwt/acre cwt/acre cwt/acre % cwt/acre cwt/acre cwt/acre
Untreated control
 --
 36
 19
 0
 55
 64
 4
 59
 151
Handweeded
 --
 87
 125
 19
 231
 33
 26
 257
 342
Sencor
 0.5
 89
 163
 29
 282
 31
 40
 322
 406
Prowl
 1.0
 82
 87
 7
 176
 42
 19
 195
 293
Dual Magnum
 1.34
 75
 88
 9
 171
 41
 18
 189
 291
Eptam
 3.0
 89
 117
 8
 214
 37
 40
 255
 338
Spartan
 0.141
 79
 156
 23
 257
 35
 44
 301
 388
Chateau
 0.094
 70
 127
 22
 220
 32
 22
 242
 315
Outlook
 0.656
 84
 148
 34
 265
 32
 36
 302
 388
Matrix
 0.023
 84
 114
 17
 215
 38
 31
 246
 342
Spartan + Sencor
 0.141+0.5
 92
 173
 26
 291
 32
 43
 334
 428
Spartan + Prowl
 0.141+1.0
 95
 188
 38
 322
 28
 50
 372
 448
Spartan+DualMagnum
 0.141+1.34 92
 138
 24
 254
 33
 41
 295
 382
Spartan + Eptam
 0.141 + 3.0
 84
 162
 39
 285
 30
 38
 323
 406
Spartan + Matrix
 0.141+0.023
 95
 158
 34
 286
 32
 49
 336
 418
Chateau + Sencor
 0.094 + 0.5
 82
 155
 31
 267
 29
 27
 294
 373
Chateau + Prowl
 0.094 + 1.0
 89
 136
 19
 244
 33
 28
 273
 364
Chateau+DualMagnum
 0.094 + 1.34
 79
 160
 42
 282
 28
 31
 312
 391
Chateau + Eptam
 0.094 + 3.0
 91
 161
 25
 287
 29
 31
 318
 402
Chateau + Matrix
 0.094+0.023 85
 176
 31
 292
 28
 42
 334
 403
Outlook + Sencor
 0.656 + 0.5
 101
 183
 35
 319
 28
 38
 357
 443
Outlook + Matrix
 0.656+0.023 97
 165
 31
 294
 31
 33
 327
 422
Spartan + Outlook
 0.141+0.656 87
 169
 33
 289
 31
 50
 339
 420
Chateau + Outlook
 0.094+0.656 89
 160
 30
 280
 28
 25
 305
 389
Prowl + Matrix
 1.0 + 0.023
 90
 180
 36
 306
29
42
348
429
Outlook + Prowl
 0.656 + 1.0
91
176
40
307
29
30
337
431
DualMagnum+Prowl
1.34 + 1.0
 100
 138
 26
 264
 32
 24
 288
385
DualMagnum+Sencor
 1.34 + 0.5
92
167
28
287
29
35
322
405
DualMagnum+Matrix
 1.34 + 0.023
 103
182
35
320
27
30
350
439
Prowl + Eptam
1.0 + 3.0
105
167
29
301
30
28
329
429
LSD (0.05)

18
36
16
54
7
13
53
52
*Herbicide treatments were applied preemergence on May 19. Chateau was reported as Valor in previous reports.
†Potatoes were harvested September 9 to11.

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