Dimethenamid-p: Efficacy and Potato (Solanum ... - PubAg - USDA

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Abstract: Treatments of dimethenamid-p at 0.7 kg ai/ha applied PRE in tank mixtures with EPTC .... spaced 86 cm apart at Washington and 91 cm apart at.

Weed Technology. 2005. Volume 19:966–971

Dimethenamid-p: Efficacy and Potato (Solanum tuberosum) Variety Tolerance1 PAMELA J. S. HUTCHINSON, COREY V. RANSOM, RICK A. BOYDSTON, and BRENT R. BEUTLER2 Abstract: Treatments of dimethenamid-p at 0.7 kg ai/ha applied PRE in tank mixtures with EPTC (3.4 kg ai/ha), metribuzin (560 g ai/ha), pendimethalin (1.1 kg ai/ha), or rimsulfuron (26 g ai/ha) were compared with the same herbicides applied PRE alone in field efficacy trials in Idaho, Oregon, and Washington. Common lambsquarters, kochia, and redroot pigweed control was generally improved with dimethenamid-p tank mixtures compared with control by any herbicide applied alone except metribuzin. Hairy nightshade control at two locations was generally improved with tank mixtures compared with control by any herbicide applied alone. At Washington, where row spacing was narrower than at other locations, dimethenamid-p alone or in tank mixtures provided similar hairy nightshade control, and this control was greater than control by EPTC, metribuzin, or pendimethalin applied alone. ‘Alturas’, ‘Bannock Russet’, ‘Ranger Russet’, ‘Russet Burbank’, ‘Russet Norkotah’, and ‘Shepody’ potato tolerance to dimethenamid-p PRE at 0, 0.7, or 1.4 kg ai/ha was assessed in weed-free field trials conducted at Aberdeen, ID, in 2002 and 2003. Little or no crop injury was evident during the growing seasons and there were no reductions in U.S. No. 1 and total tuber yields regardless of dimethenamid-p rate or potato variety. Nomenclature: Dimethenamid; dimethenamid-p; EPTC; metribuzin; pendimethalin; rimsulfuron; potato, Solanum tuberosum L. ‘Alturas’, ‘Bannock Russet’, ‘Ranger Russet’, ‘Russet Burbank’, ‘Russet Norkotah’, ‘Shepody’, ‘Superior’; barnyardgrass, Echinochloa crus-galli (L.) Beauv #3 ECHCG; common lambsquarters, Chenopodium album L. # CHEAL; hairy nightshade, Solanum sarrachoides Sendter # SOLSA; kochia, Kochia scoparia (L.) Shrad. # KCHSC; redroot pigweed, Amaranthus retroflexus L. # AMARE; volunteer oat, Avena sativa L. # AVESA. Additional index words: Crop safety, crop tolerance, herbicide efficacy, herbicide injury. Abbreviations: OM, organic matter; PNW, Pacific Northwest; TMP, tank-mix partner; WAT, weeks after treatment.

INTRODUCTION

sulfuron or sulfentrazone, provide acceptable seasonlong hairy nightshade control (Guttieri and Eberlein 1997; Hutchinson 2004; Hutchinson and Eberlein 2003; Hutchinson et al. 2002). Hairy nightshade control with rimsulfuron has been inconsistent (Eberlein et al. 1994, 1996; Guttieri and Eberlein 1997; Hutchinson and Eberlein 2003). Sugar beet (Beta vulgaris L.), a rotational crop common in many potato production areas, may not be planted the season following rimsulfuron use in potato and not for 36 months after sulfentrazone use (Anonymous 2000; Anonymous 2004b). There are no sugar beet rotational restrictions the year following dimethenamid-p application in potato (Anonymous 2004a), and dimethenamidp can provide 90% or greater season-long hairy nightshade control (Hutchinson et al. 2002). Dimethenamid has provided greater than 96% control of hairy nightshade, common lambsquarters, and redroot pigweed in past Idaho research trials at rates of 1.1 to 1.7 kg/ha (Tonks et al. 1999). However, common lambs-

Dimethenamid-p, the formulated active isomer of the herbicide dimethenamid (Courdechet et al. 1997), is a chloroacetamide that controls many annual broadleaf and grass weeds when applied PRE and was registered for use in potato in 2005 (Anonymous 2004a; Hutchinson et al. 2004). In Pacific Northwest (PNW) potato production areas, hairy nightshade is a prevalent weed. Only two of the other eight herbicides registered before 2005 in the PNW for broadleaf weed control in potato, rim1 Received for publication November 3, 2004, and in revised form April 19, 2005. Paper 04P06 University of Idaho Agricultural Experiment Station. 2 Assistant Professor, Department of Plant, Soil, and Entomological Sciences, University of Idaho, Aberdeen, ID, 83210; Assistant Professor, Malheur Experiment Station, Oregon State University, Ontario, OR, 97914; Agronomist, USDA-ARS, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350; Former Research Support Scientist I, Aberdeen Research and Extension Center, Aberdeen, ID 83210. Corresponding author’s E-mail: [email protected] 3 Letters following this symbol are a WSSA-approved computer code from Composite List of Weeds, Revised, 1989. Available only on computer disk from WSSA, 810 East 10th Street, Lawrence, KS 66044-8897.

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quarters control by PRE-applied dimethenamid at rates up to 1.7 kg/ha or dimethenamid-p at 0.7 kg/ha was similar and did not exceed 68% in a Virginia trial (Richardson et al. 2004). Russet Burbank is the major potato variety planted in the United States accounting for approximately 46% of U.S. hectarage in 2002, while Russet Norkotah, Ranger Russet, and Shepody were the other top varieties planted in 2002 accounting for 12, 9, and 7%, respectively. (Anonymous 2002). Although increasing dimethenamid rates to 3.4 kg/ha caused increasing Russet Burbank injury, and increasing rates to 1.7 kg/ha resulted in greater injury to Superior compared with injury caused by 0.84 kg ai/ha in previous studies, marketable tuber yield of either variety was not affected (Richardson et al. 2004; Tonks et al. 1999). Superior was tolerant to PRE-applied dimethenamid-p at 0.7 kg/ha. In past dimethenamid-p tolerance trials conducted in the PNW, Russet Burbank was tolerant to rates as high as 2.9 kg ai/ha (Hutchinson et al. 2004). Because little information is available for weed control in potato with dimethenamid-p, or for tolerance of major varieties other than Russet Burbank, the objectives of this research were to evaluate weed control in potato with dimethenamid-p applied PRE alone or in tank mixtures with standard potato herbicides and to determine tolerance of six potato varieties to dimethenamid-p at 0, 0.7, or 1.4 kg/ha dimethenamid-p. MATERIALS AND METHODS

Idaho efficacy trials were conducted at the University of Idaho Aberdeen Research and Extension Center near Aberdeen, ID, in 2001 to 2003; near Paterson, Washington in 2001; and at the Oregon State University Malheur Experiment Station near Ontario, Oregon, in 2003. The soil type at Idaho was a Declo loam (coarse-loamy, mixed, mesic, Xerollic Calciorthids) with 1.4% organic matter (OM)and pH 8.0. The Washington trial was conducted on a Quincy sand (Typic Torripsamments) with 0.5% OM and pH 7.0. The soil type for Oregon was an Owyhee silt-loam (coarse-silty, mixed, mesic Xerollic Camborthids) with 1.6% OM and pH 7.0. The dimethenamid-p efficacy trial experimental design each year was a randomized complete block with three or four replications depending on location. Plot size was 3.7 m wide by 9.1 to 13.7 m long. Russet Burbank potato seed pieces were planted at 25-cm intervals in rows spaced 86 cm apart at Washington and 91 cm apart at Idaho and Oregon. The crop was hilled just before, or up to 10% emergence (standard grower practice). TreatVolume 19, Issue 4 (October–December) 2005

ments included dimethenamid-p applied alone or in twoway tank mixtures at 0.7 kg/ha with EPTC (3.4 kg/ha), metribuzin (56 g/ha), pendimethalin (1.1 kg/ha), or rimsulfuron (26 g/ha). The tank-mix partners also were applied alone in separate treatments. Herbicides were applied with either a CO2-pressurized back-pack or bicycle sprayer with 8002 VS flat fan nozzles4 that delivered 160 to 190 L/ha. Applications were made just after hilling and before potato reemergence, and herbicides were incorporated with sprinkler irrigation delivering 2 cm of water immediately after application. Potato variety response to dimethenamid-p at 0.7 or 1.4 kg/ha was evaluated at the Idaho location in 2002 and 2003. A nontreated control of each variety was included. Alturas, Bannock Russet, Ranger Russet, Russet Burbank, Russet Norkotah, and Shepody were planted in a split-block design with variety as the main plot and dimethenamid-p rate (0, 0.7, or 1.4 kg/ha) as the subplot. Herbicide treatments were applied and incorporated in a similar manner as in the efficacy trials. The trial area was kept weed-free throughout each growing season by periodic hand weeding. Tubers were mechanically harvested from 7.6 m of each of the center two rows of each plot in all trials approximately two wk after vine kill. Planting, application, and harvest dates for all trials and weed densities in the efficacy trials are listed in Table 1. The efficacy and variety tolerance trials at all locations were irrigated as needed, with center pivot at Washington and solid set sprinklers at Idaho and Oregon, to maintain a minimum soil water content of 65% field capacity. The experimental areas were fertilized according to soil test recommendations before planting and additional nitrogen fertilizer was applied through the irrigation system throughout each growing season based on petiole analyses. Ratings, Yields, and Data Analysis. Weed control in the efficacy trials was evaluated visually using a scale of 0 to 100% where 0 equals no control and 100 was complete control approximately 2 wk after treatment (WAT), at row closure (4 to 6 WAT), and just before vine-kill (preharvest). The preharvest rating represents season-long weed control and is shown in all tables. Potato injury in the efficacy and variety tolerance trials was evaluated visually on a scale of 0 (no injury) to 100% (complete death) approximately 2 WAT, at row closure (approximately 4 to 6 WAT), and 8 WAT. Height mea4 8002 VS flat fan nozzles, Spraying Systems Co., P.O. Box 7900, Wheaton, IL 60189.

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Table 1. Planting, herbicide application, harvest dates, and weed densities of efficacy trials at Aberdeen, ID, on 2001, 2002, and 2003; at Paterson, WA, in 2001; and at Ontario, OR, in 2003; and variety tolerance trials at Aberdeen, ID, in 2002 and 2003. Date Location

Year

Planting

Weed densitya

Application

Harvest

AMARE

CHEAL

KCHSC

SOLSA

AVESA

ECHCG

9 1 4 — —

—b — — — 11

plants/m

2

Idaho Washington Oregon Idaho variety trials

2001 2002 2003 2001 2003 2002 2003

5/01 4/30 4/30 3/30 4/24 5/08 5/12

5/22 5/23 5/22 4/30 5/19 6/03 5/30

9/18 9/16 9/24 8/20 9/10 10/03 10/06

40 90 80 30 43

40 20 10 — 73

9 9 4 — 20

100 90 100 100 22

a Abbreviations: AMARE, redroot pigweed; CHEAL, common lambsquarters; KCHSC, kochia; SOLSA, hairy nightshade; AVESA, volunteer oat; ECHCG, barnyardgrass. b — indicates the weed was not present at that location.

surements of 10 randomly selected plants in the two center rows of each plot were recorded in the variety tolerance trials 2, 5, and 8 WAT. Total tuber yield was recorded, and yield by grade according to USDA standards were determined for U.S. No. 1 tubers (tubers with no defects weighing at least 113 g). An ANOVA was performed using PROC GLM (PCSAS5). Arcsine transformations were used on percentage of weed control and crop injury when needed to mitigate the skewness of the data and meet the requirements of normality for analysis. Nontreated control data were not included in the weed control or crop injury analysis and were included for height and tuber yield comparisons. 5

PC-SAS softwaret, SAS Institute, Box 8000, Cary, NC 27511.

Table 2. Season-long common lambsquarters, kochia, and redroot pigweed control at Aberdeen, ID in 2001, 2002, and 2003, and Ontario, OR in 2003 with dimethenamid-p and four other herbicides applied PRE alone or in tank mixtures.a

RESULTS AND DISCUSSION

Controlb Treatmentc

Common lambsquarters

Kochia

Redroot pigweed

% Dimethenamid-p EPTC Metribuzin Dimethenamid-p 1 metribuzin Pendimethalin Dimethenamid-p 1 pendimethalin Rimsulfuron Dimethenamid-p 1 rimsulfuron

81 c 81 c 96 a 99 a 75 c 99 a 75 c 91 b

89 c 61 d 98 a 99 a 89 c 97 ab 84 c 94 b

88 c 70 d 96 ab 97 a 53 e 94 bc 92 bc 97 ab

a The location–year by treatment interactions for common lambsquarters, kochia, or redroot pigweed control data were not significant (P . 0.05). b Treatment means within a column followed by the same letter are not significantly different according to Fisher’s Protected LSD test (P 5 0.05) performed on arcsine transformed data. Nontransformed data are reported in this table. c Rates alone or in tank mixtures: dimethenamid-p 0.7 kg/ha; EPTC 3.4 kg/ ha; metribuzin 560 g/ha; pendimethalin 1.1 kg/ha; rimsulfuron 26 g/ha. The dimethenamid-p 1 EPTC treatment was not included at Oregon, so this treatment was not included in the statistical analysis.

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Fisher’s Protected LSD tests (P 5 0.05) were used for separation of efficacy trial treatment means and for the injury data from the variety tolerance study. Orthogonal contrasts were performed to determine the effect of dimethenamid-p rate on potato plant height and tuber yields in the variety tolerance study. If the rate effect was significant, trend contrasts were performed to determine if the response was linear or quadratic. For statistical purposes, each location and year in the efficacy trials was defined as an environment and only treatments common to all environments were included for analyses. Efficacy data were combined over environments when environment by treatment interactions were not significant at P 5 0.05. Variety tolerance data were combined over years when year by rate by variety, year by rate, or year by variety interactions were not significant at P 5 0.05.

Weed Control. Potato crop injury in the efficacy trials was less than 5% regardless of year, location, or treatment (data not shown). Common lambsquarters, kochia, and redroot pigweed were present all years of testing at Idaho and Oregon, and because the environment by treatment interactions were not significant (P . 0.05) for control of those weeds, those data were pooled (Table 2). Dimethenamid-p, EPTC, pendimethalin, or rimsulfuron applied alone controlled common lambsquarters and kochia 75 to 81% and 61 to 89%, respectively. Tank mixtures of dimethenamid-p plus metribuzin, pendimethalin, or rimsulfuron provided improved control of common lambsquarters (91 to 99%) and kochia (94 to 99%) compared with control by dimethenamid-p, EPTC, pendimethalin, or rimsulfuron applied alone, but not by metribuzin applied alone (Table 2). These results are similar Volume 19, Issue 4 (October–December) 2005

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Table 3. Season-long hairy nightshade (SOLSA) control with dimethenamidp and four other herbicides applied PRE alone or in tank mixtures at Aberdeen, ID, in 2001, 2002, and 2003; at Paterson, WA, in 2001; and at Ontario, OR, in 2003.a

Table 4. Season-long volunteer oat (AVESA) control at Aberdeen, ID, in 2001, 2002, and 2003, and barnyardgrass control at Ontario, OR, in 2003, with dimethenamid-p and four other herbicides applied PRE alone or in tank mixtures.a

Hairy nightshade controlb Idaho Washington (2001–2003) (2001)

Treatmentc

Oregon (2003)

% Dimethenamid-p EPTC Dimethenamid-p Metribuzin Dimethenamid-p Pendimethalin Dimethenamid-p Rimsulfuron Dimethenamid-p

1 EPTC 1 metribuzin 1 pendimethalin 1 rimsulfuron

88 c 71 d 96 b 37 e 98 a 17 f 93 b 86 c 95 b

97 b 92 c 99 ab 73 d 97 ab 87 c 99 ab — 100 a

90 b 94 ab —d 95 ab 100 a 89 b 100 a 92 b 100 a

The location–year by treatment interaction was significant for SOLSA control (P , 0.05) when all location–year data were combined. The year by treatment interaction was not significant for 2001, 2002, and 2003 data at Idaho, so those data were pooled over years. b Treatment means within a column followed by the same letter are not significantly different according to Fisher’s Protected LSD test (P 5 0.05) performed on arcsine transformed data. Nontransformed data are reported in this table. c Rates alone or in tank mixtures: dimethenamid-p 0.7 kg/ha; EPTC 3.4 kg/ ha; metribuzin 560 g/ha; pendimethalin 1.1 kg/ha; rimsulfuron 26 g/ha. d — indicates the treatment was not included at that location. a

to an improvement in common lambsquarters control by dimethenamid-p applied PRE with metribuzin or followed by a postemergence rimsulfuron application compared with control by dimethenamid-p applied alone in a Virginia trial (Richardson et al. 2004). Common lambsquarters and kochia control by metribuzin was not improved compared with the dimethenamid-p and metribuzin tank mixture. Although the data are not shown because the dimethenamid-p plus EPTC tank mixture was not included in the Oregon trial, common lambsquarters and kochia control was greater with this combination than either herbicide applied alone at Idaho. The combination of dimethenamid-p with metribuzin or pendimethalin provided greater control of these two weeds than dimethenamid-p plus rimsulfuron (and dimethenamid-p plus EPTC in Idaho). Redroot pigweed control with dimethenamid-p alone was similar to control with dimethenamid-p plus pendimethalin or rimsulfuron, however, all tank mixtures improved redroot pigweed control compared with EPTC or pendimethalin applied alone (Table 2). Dimethenamid-p plus pendimethalin or rimsulfuron did not control redroot pigweed better than rimsulfuron applied alone. Redroot pigweed also was present at Washington, and all treatments except metribuzin alone provided 95% or better control (data not shown). When hairy nightshade control data from all environVolume 19, Issue 4 (October–December) 2005

Controlb Treatmentc

Volunteer oat

Barnyardgrass %

Dimethenamid-p EPTC Dimethenamid-p Metribuzin Dimethenamid-p Pendimethalin Dimethenamid-p Rimsulfuron Dimethenamid-p

1 EPTC 1 metribuzin 1 pendimethalin 1 rimsulfuron

88 cd 83 d 93 ab 90 bc 96 a 84 d 95 a 89 c 95 a

98 ab 98 ab —d 96 abc 100 a 74 bc 98 ab 69 c 100 a

a The year by treatment interaction for AVESA control at Idaho in 2001, 2002, and 2003 was not significant (P . 0.05), so those data are shown pooled over years. b Treatment means within a column followed by the same letter are not significantly different according to Fisher’s Protected LSD test (P 5 0.05) performed on arcsine transformed data. Nontransformed data are reported in this table. c Rates alone or in tank mixtures: dimethenamid-p 0.7 kg/ha; EPTC 3.4 kg/ ha; metribuzin 560 g/ha; pendimethalin 1.1 kg/ha; rimsulfuron 26 g/ha. d — indicates the treatment was not included at that location.

ments were combined, the environment by treatment interaction was significant (P , 0.05), however, when Idaho data were combined across years, the year by treatment interaction was not significant, so the data are shown pooled across years for Idaho and separately for Washington (2001) and for Oregon (2003) in Table 3. At Idaho, all tank mixtures improved hairy nightshade control to at least 93% compared with 17 to 88% control by dimethenamid-p or any of the tank-mix partners (TMPs) applied alone. Results were similar at Oregon, except that hairy nightshade control with any tank mixture at 100% was not greater than with metribuzin alone at 95%. At Washington, where row spacing was narrower and the potato crop was more competitive than in Idaho or Oregon, only the dimethenamid-p plus rimsulfuron tank mixture provided greater control than dimethenamid-p alone (Table 3). Similar to Idaho and Oregon results, however, the tank mixtures at Washington improved hairy nightshade control compared with control by EPTC, metribuzin, or pendimethalin applied alone. Volunteer oat control by tank mixtures at Idaho was improved to 95% or greater compared with the 89% or less control by dimethenamid-p or any TMP applied alone, with the exception of control by dimethenamid-p plus EPTC at 93% compared with metribuzin applied alone at 90% (Table 4). Although barnyardgrass control at Washington by dimethenamid-p plus metribuzin or 969

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Table 5. Effect of dimethenamid-p and four other herbicides applied preemergence (PRE) alone or in tank mixtures at Aberdeen, ID, in 2001 and 2002; Paterson, WA, in 2001; and Ontario, OR, in 2003, on U.S. No. 1 and total tuber yield.a Tuber yieldb Idaho 2001 and 2003 Treatmentc

U.S. No. 1

Total

Idaho 2002 U.S. No. 1

Total

Washington 2001 U.S. No. 1

Oregon 2003

Total

U.S. No. 1

Total

55.4 b 76.9 a 75.0 a 80.7 a 68.4 ab 74.3 a 70.1 a 64.5 ab 73.5 a — 69.6 a

6.2 e 25.9 bcd 29.8 abc 24.0 cd —d 31.6 ab 35.8 a 19.7 d 34.4 a 24.1 cd 32.9 a

16.9 e 38.3 cd 43.5 bc 37.9 cd — 45.5 ab 49.7 a 32.9 d 48.3 ab 38.3 cd 47.3 ab

MT/ha Nontreated control Weed-free control Dimethenamid-p EPTC Dimethenamid-p 1 Metribuzin Dimethenamid-p 1 Pendimethalin Dimethenamid-p 1 Rimsulfuron Dimethenamid-p 1

EPTC metribuzin pendimethalin rimsulfuron

8.7 c 21.1 a 20.7 a 17.9 ab 21.2 a 22.7 a 23.4 a 11.6 bc 24.3 a 23.3 a 24.7 a

17.8 b 32.3 a 31.6 a 29.0 a 33.4 a 33.8 a 34.9 a 20.3 b 35.2 a 34.7 a 36.7 a

8.4 d 42.0 a 32.5 c 28.5 c 30.0 c 35.7 abc 33.7 bc 10.4 d 40.8 ab 32.2 c 40.0 ab

13.9 f 53.3 ab 41.8 de 37.4 e 44.6 cd 50.7 abc 51.6 abc 15.5 f 52.0 ab 46.7 bcd 53.9 a

47.3 b 71.4 a 66.3 a 72.9 a 59.2 ab 64.2 a 61.2 ab 59.5 ab 64.3 a — 62.2 a

a The location–year by treatment interaction was significant for U.S. No. 1 and total tuber yield (P , 0.05) when all location–year data were combined. The year by treatment interactions for data from Aberdeen, ID, in 2001, 2002, and 2003 was not significant (P . 0.05), so those data are reported in this table pooled over years. b Treatment means within a column followed by the same letter are not significantly different according to Fisher’s Protected LSD test (P 5 0.05). U.S. No. 1 tubers had no defects and weighed at least 113 g. c Rates alone or in tank mixtures: dimethenamid-p 0.7 kg/ha; EPTC 3.4 kg/ha; metribuzin 560 g/ha; pendimethalin 1.1 kg/ha; rimsulfuron 26 g/ha. d — indicates the treatment was not included at that location.

rimsulfuron at 100% was greater than by pendimethalin or rimsulfuron applied alone at 74 or 69%, respectively, no other tank mixture improved control compared with dimethenamid-p or any other TMP applied alone (Table 4). The environment by treatment interactions for U.S. No. 1 and total tuber yield data were significant when all environments were combined (P , 0.05) (Table 5). At Idaho in 2001 and 2003, the year by treatment interactions for tuber yields were not significant, so those data were pooled, whereas Idaho 2002, Washington 2001, and Oregon 2003 yield data are shown separately in Table 5. Yields in Washington and Oregon were numerically greater than in Idaho, as would be expected, because the growing season in Washington and Oregon is longer than at the eastern Idaho trial location. Yields in 2001 and 2003 were generally less than in 2002 at Idaho most likely because of heat stress occurring in 2001 and 2003. At Idaho in 2002, as with weed control, tuber yields resulting from tank mixtures of dimethenamid-p with pendimethalin or rimsulfuron were greater than tuber yields from those herbicides applied alone (Table 5). Tuber yields also improved similarly in Oregon in 2002, however, those tank mixtures did not result in yields greater than yields with dimethenamid-p applied alone. The yield impact of less weed control by dimethenamidp alone compared with control by tank-mixtures may not 970

have been as great in Oregon because overall weed density was slightly less in Oregon than in Idaho. In 2001 and 2003 at Idaho, yields resulting from tank mixtures were not greater than yields resulting from dimethenamid-p or any TMP applied alone except pendimethalin. Difference in weed control when comparing the tank mixtures to dimethenamid-p or most of the TMPs applied alone may not have translated to significant differences in yields at Idaho in 2001 and 2003 when heat stress may have been more limiting than weed competition. At Washington, where the potato crop was more competitive because row spacing was narrower than it was in Idaho or Oregon, all treatments resulted in yields similar to weed-free yields, and tank-mixture yields were not greater than yields resulting from dimethenamid-p or any TMP applied alone (Table 5). Variety Tolerance. In 2002, no injury was observed during the growing season regardless of herbicide rate or potato variety (data not shown). In 2003, at 2 WAT, however, one of the six varieties tested, Alturas, exhibited 8 or 13% injury caused by dimethenamid-p at 0.7 or 1.4 kg/ha, respectively (data not shown). Injury to this variety consisted mainly of stunting. No injury was observed in the other varieties at 2 WAT, and no injury was observed during the remainder of the season regardless of rate or variety. Because the varieties tested usually grow to different heights, height measurements Volume 19, Issue 4 (October–December) 2005

WEED TECHNOLOGY

were analyzed by variety. Although the rate effect was not significant (P . 0.05), there was a trend for decreased height of Alturas in 2003 at 2 and 5 WAT as dimethenamid-p rate increased (data not shown). The year by rate by variety, or rate by variety interactions for U.S. No. 1 and total tuber yield data were not significant (P . 0.05). As would be expected, tuber yields were different depending on variety, and averaged across herbicide rate, U.S. No. 1 and total tuber yields ranged from 20.1 to 31.5 and 30.9 to 40.8 MT/ha, respectively (data not shown). However, even though one of the six varieties tested exhibited significant early season injury, the rate effect was not significant for tuber yield data, and averaged across the six varieties tested, U.S. No. 1 and total tuber yield ranged from 23.7 to 28.3 MT/ha and 32.8 to 38.7 MT/ha (data not shown). These results are in agreement with previous research where 0.7, 1.4, or 2.9 kg/ha dimethenamid-p applied PRE did not cause yield reductions of Russet Burbank in weedfree tolerance trials (Hutchinson et al. 2004). Overall, dimethenamid-p combined with EPTC, metribuzin, pendimethalin, or rimsulfuron in PRE-applied, two-way tank mixtures can provide season-long control of hairy nightshade and many other weeds found in potato fields. Depending on weed density, crop competitiveness, and TMP, control with these mixtures is improved compared with control by dimethenamid-p or the TMP applied alone. Dimethenamid-p has good crop safety as seen with the six potato varieties tested in the Idaho tolerance trials. Most crops grown in rotation with potato, including sugar beets, can be planted the year following dimethenamid-p use in potato, so the herbicide will be a good fit in many potato weed management programs. ACKNOWLEDGMENTS

The authors gratefully acknowledge the technical assistance of Felix E. Fletcher, Daniel Hancock, Joey K.

Volume 19, Issue 4 (October–December) 2005

Ishida, and Marc Seymour and the statistical analyses assistance from Bill Price. This research was supported in part by the Idaho Potato Commission, the Oregon Potato Commission, and BASF Corporation. LITERATURE CITED Anonymous. 2000. Matrixt herbicide product label. DuPont Publication No. H-63849. Wilmington, DE: DuPont. 5 p. Anonymous. 2002. Potato statistics (91011). Table 67—Fall Potatoes: Percent of major varieties planted, selected states, 1984–02. U.S. Department of Agriculture Economic Research Service. Web page: http:// www.ers.usda.gov/data/sdp/view.asp?f5specialty/91011/. Accessed: September 6, 2005. Anonymous. 2004a. Outlookt herbicide product label. BASF Publication No. NVA-2004-04-086-03136. Research Triangle Park, NC: BASF Corporation. 20 p. Anonymous. 2004b. Spartant herbicide product label. FMC Publication No. Spartanp3p03-31-2004(Field). Philadelphia, PA: FMC Corporation. 13 p. Courdechet, M., P. F. Bocoin, R. Chollet, K. Seckinger, and P. Boger. 1997. Biological activity of two stereoisomers of the N-thienyl chloroacetamide herbicide dimethenamid. Pest. Sci. 50:221–227. Eberlein, C. V., C. W. Kral, and M. J. Guttieri. 1996. Using Matrix in weed management systems for potatoes. CIS No. 1037. Moscow, ID: University of Idaho Agricultural Communications. 8 p. Eberlein, C. V., J. C. Whitmore, C. E. Stanger, and M. J. Guttieri. 1994. Postemergence weed control in potatoes (Solanum tuberosum) with rimsulfuron. Weed Technol. 8:428–435. Guttieri, M. J. and C. V. Eberlein. 1997. Preemergence weed control in potatoes (Solanum tuberosum) with rimsulfuron mixtures. Weed Technol. 11:755–761. Hutchinson, P.J.S. 2004. Potatoes. In R. D. William, D. Ball, T. L. Miller, R. Parker, J. P. Yenish, T. W. Miller, D. W. Morishita, and P.J.S. Hutchinson, eds. Pacific Northwest 2004 Weed Management Handbook. Corvallis, OR: PNW Public Cooperative Extension System. Pp 177–189. Hutchinson, P.J.S. and C. V. Eberlein. 2003. Weed management. In Potato Production Systems. J. C. Stark and S. L. Love, eds. Moscow, ID: University of Idaho Agricultural Communications. Pp. 241–283. Hutchinson, P.J.S., C. V. Ransom, D. J. Tonks, and C. V. Eberlein. 2004. Russet Burbank potato (Solanum tuberosum) tolerance to dimethenamidp. Weed Technol. 18:850–852. Hutchinson, P.J.S., D. J. Tonks, and F. E. Fletcher. 2002. Weed control with developmental preemergence herbicides in potatoes. In 2002 Research Progress Report. Newark, CA: Western Society of Weed Science. Pp. 34–35. Richardson, R. J., C. M. Whaley, H. P. Wilson, and T. E. Hines. 2004. Weed control and potato (Solanum tuberosum) tolerance with dimethenamid isomers and other herbicides. Am. J. Potato Res. 81:299–304. Tonks, D. J., C. V. Eberlein, M. J. Guttieri, and B. A. Brinkman. 1999. SAN 582 efficacy and tolerance in potato (Solanum tuberosum). Weed Technol. 13:71–76.

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