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Crop Protection 26 (2007) 1755–1758

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Effect of s-metolachlor application timing on cabbage tolerance

Peter H. Sikkemaa, Nader Soltania,�, William Deenb, Darren E. Robinsona

aUniversity of Guelph Ridgetown Campus, 120 Main Street East, Ridgetown, Ont., Canada N0P 2C0bDepartment of Plant Agriculture, University of Guelph, Guelph, Ont., Canada N1G 2W1

Received 15 March 2007; accepted 16 March 2007

Abstract

There is limited information on the effect of s-metolachlor application timing on cabbage tolerance in Ontario. A total of five field

trials (1999–2004) were established near Ridgetown Ontario, Canada to evaluate tolerance of cabbage to s-metolachlor applied pre-

transplant incorporated, pre-transplant and post-transplant at 800, 1600 and 2400 g a.i./ha. s-Metolachlor applied pre-transplant

incorporated, pre-transplant and post-transplant at 800, 1600 and 2400 g a.i./ha did not have any effect on visual injury, marketable head

production, marketable head weight and yield of cabbage. There was also no difference among s-metolachlor application timings (pre-

transplant incorporated, pre-transplant and post-transplant) in respect to cabbage tolerance. Based on these results s-metolachlor

applied pre-transplant incorporated, pre-transplant and post-transplant at 800, 1600 and 2400 g a.i./ha has an acceptable level of crop

safety in cabbage.

r 2007 Elsevier Ltd. All rights reserved.

Keywords: Application timing; Cabbage; Sensitivity; s-Metolachlor

1. Introduction

Cabbage is an increasingly important cash crop forgrowers in south western Ontario. In 2004, growers inOntario planted approximately 1300 ha of cabbage andproduced more than 47,000,000 kg of cabbage with a farmgate value of over $10 million (Mailvaganam, 2005).Effective weed management is essential to optimizecabbage yield. Weed control in cabbage production inOntario is currently limited to a small number of registeredherbicides. The pre-transplant herbicides registered for usein this crop in Ontario (trifluralin, chlorthal dimethyl andnapropamide) do not provide adequate season long controlof Cyperus esculentus (yellow nutsedge) and Solanum

species. More research is needed to identify herbicides tocontrol these weeds that have an adequate margin of cropsafety in cabbage in Ontario.

s-Metolachlor is a chloroacetamide herbicide that can beapplied early pre-transplant incorporated, pre-transplant,or post-transplant to control annual grass and broadleaved

e front matter r 2007 Elsevier Ltd. All rights reserved.

opro.2007.03.006

ing author. Tel.: +1519 674 1645; fax: +1 519 674 1600.

ess: nsoltani@ridgetownc.uoguelph.ca (N. Soltani).

weeds. s-Metolachlor is absorbed by germinating grassesmainly through the shoot just above the seed and inbroadleaved weeds through the root and the shoot.Susceptible grass species in s-metolachlor-treated soils failto emerge or show malformed and twisted seedlings withleaves rolled in the whorl (Vencill, 2002). Susceptiblebroadleaved species will have chlorotic and necrotic leavesand often have growth reduction (Vencill, 2002).

s-Metolachlor can effectively control troublesome weedssuch as Setaria faberii Herrm. (giant foxtail), Setaria viridis

(L.) Beauv. (green foxtail), Setaria glauca (L.) Beauv.(yellow foxtail), Digitaria sanguinalis (L.) Scop. (largecrabgrass), Digitaria ischaemum (Schreb) Muhl. (smoothcrabgrass), Echinochloa crusgalli (L.) Beauv. (barnyard-grass), Panicum dichotomiflorum Michx. (fall panicum),Panicum capillare L. (witchgrass), C. esculentus (yellownutsedge), Amaranthus retroflexus L. (redroot pigweed),Solanum americanum (American black nightshade) andSolanum ptycanthum (eastern black nightshade) (OMA-FRA, 2006; Vencill, 2002).There is limited information on the effect of s-metola-

chlor application timing on cabbage tolerance in Ontario.Currently, s-metolachlor may only be applied 1–2 days

ARTICLE IN PRESS

Table 2

Effect of various application timings and doses of s-metolachlor on

cabbage visual injury at 7, 14, and 28 days after treatment (DAT) in

Ridgetown, Ontario, Canada

s-metolachlor timing Dose (g a.i./ha) Visual injury (%)

P.H. Sikkema et al. / Crop Protection 26 (2007) 1755–17581756

after transplanting cabbage. Availability of s-metolachloras a pre-transplant incorporated and pre-transplant herbi-cide for cabbage production would provide growers withan excellent tool for the control of economically importantweed species and the opportunity to spread their work loadearly in the season.

The objective of this research was to evaluate thetolerance of cabbage to s-metolachlor when applied pre-transplant incorporated, pre-transplant and post-trans-plant at 800, 1600 and 2400 g a.i./ha under Ontarioenvironmental conditions.

2. Materials and methods

Field experiments were conducted at the University ofGuelph, Ridgetown Campus, Ridgetown, Ontario, in 1999,2000, 2001, 2003 and 2004. The soil characteristics for eachtrial are described in Table 1. Each experiment wasarranged in a randomized complete block design withtreatments replicated four times. Treatments included anon-treated weed-free control and s-metolachlor appliedpre-transplant incorporated, pre-transplant and post-trans-plant at 800, 1600 and 2400 g a.i./ha.

Plots were 6m wide� 8m long. Cabbage (cv. BayouDynasty) was planted in late May of each year at the rateof 14,850 plants/ha in rows spaced 1.5m apart. The in-rowspacing was 45 cm. Plots were maintained weed-free byinter-row cultivation and hand hoeing as required.

Pre-transplant incorporated herbicide applications weremade 1–2 days before transplanting and were immediatelyincorporated into the soil with two passes (in oppositedirections) of an S-tine cultivator with rolling basketharrows. Pre-transplant herbicide applications were ap-plied to the soil surface 1–2 days before transplanting andpost-transplant applications were applied 1–2 days aftertransplanting. Spray applications were applied with a CO2-pressurized backpack sprayer, calibrated to deliver 200 l/hawith XR8002VS (Teejet XR8002VS Tip, Spraying SystemsCo., North Ave & Schmale Rd, Wheaton, IL 60188) flat-fan nozzles at 207 kPa pressure.

Crop injury was rated on a scale of 0–100% at 7, 14, and28 days after transplanting (DAT). A rating of 0% wasdefined as no visible effect of the herbicide, and 100% wasdefined as plant death. Cabbage was harvested by hand inlate July to late August of each year as they matured. The

Table 1

Soil characteristics for study sites in 1999, 2000, 2001, 2003 and 2004

Year pH OM (%) Soil texture

Sand (%) Silt (%) Clay (%)

1999 6.2 4.4 55 29 15

2000 6.9 5.3 48 34 18

2001 7.1 3.6 59 23 18

2003 7.2 6.1 73 15 12

2004 6.5 5.8 46 31 23

middle 6m of each plot was harvested by hand as cabbageheads reached maturity and the weight of each head andthe total number of heads per plot were recorded.All data were subjected to analysis of variance using the

PROCMIXED procedure of SAS, version 8.0 (SAS, 1999).Variances of visual injury at 7, 14 and 28 DAT, headnumber, head weight and yield were partitioned into thefixed effects of herbicide treatment and the random effectsof year and the year-by-treatment interaction. Significanceof random effects was tested using a Z-test of the varianceestimate and fixed effects were tested with F-tests. Errorassumptions of the variance analyses (random, homoge-neous distribution of error terms and normality) wereconfirmed using residual plots and the Shapiro–Wilknormality test. As there were no significant effects of yearor the year-by-treatment interaction, data were combinedover all the years of the study for the analysis. Tonormalize the data, visual injuries were subjected to anarcsine square root transformation (Bartlett, 1947), andhead number and weight were log transformed (Kuehl,1994). Yield data were not transformed. Orthogonalcontrasts were constructed for each variable to determineif there were significant differences between each herbicidetreatment and the non-treated control (a ¼ 0.05). Visualinjury, head number and head weight were converted backto the original scale for the presentation of results.

3. Results and discussion

3.1. Visual injury

Visual injury was similar at 7, 14, and 28 DAT.s-Metolachlor applied pre-transplant incorporated, pre-transplant and post-transplant at 800, 1600 and 2400ga.i./hacaused minimal visual injury (3% or less) to transplantedcabbage at 7, 14 and 28 DAT (Table 2). Results are similarto other studies with another cholorocetamide herbicides,dimethenamid-p at 750 and 1500 g a.i./ha in cabbage which

7 DAT 14 DAT 28 DAT

Pre-transplant incorporated 800 2 0 0

1600 3 0 0

2400 1 0 0

Pre-transplant 800 2 0 0

1600 2 1 0

2400 3 0 0

Post-transplant 800 3 1 0

1600 2 0 0

2400 0 0 0

SE (7) 2 1 0

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Table 3

Effect of various application timings and doses of s-metolachlor on cabbage marketable head production, marketable head dry weight, and yield of

cabbage in Ridgetown, Ontario, Canada

Herbicide Dose (g a.i./ha) Number of heads (#/plot) Head dry weight (g) Yield (tons/ha)

Pre-transplant incorporated 800 11 2413 26.4

1600 12 2255 23.4

2400 13 2421 25.7

Pre-transplant 800 12 2386 26.7

1600 11 2540 27.1

2400 12 2460 25.4

Post-transplant 800 11 2310 24.5

1600 11 2556 26.4

Non-treated control 2400 12 2676 27.7

11 2465 25.9

SE (7) 2 334 2.3

P.H. Sikkema et al. / Crop Protection 26 (2007) 1755–1758 1757

caused no visual injury in cabbage in Ontario (Sikkema etal., 2007). When injury was observed, symptoms includedstunting, and chlorosis and necrosis of the leaves.

3.2. Marketable head number

s-Metolachlor applied pre-transplant incorporated, pre-transplant and post-transplant at 800, 1600 and 2400ga.i./hadid not change cabbage marketable head number com-pared to the non-treated control (Table 3). These resultsare similar to other studies with dimethenamid-p at 750and 1500 g a.i./ha, which caused no change in cabbage headnumber (Sikkema et al., 2007).

3.3. Marketable head weight

Cabbage marketable head weight was similar to the non-treated control at all three doses of s-metolachlor whenapplied pre-transplant incorporated, pre-transplant andpost-transplant (Table 3).

3.4. Yield

s-Metolachlor applied pre-transplant incorporated, pre-transplant and post-transplant at 800, 1600 and 2400ga.i./hadid not change cabbage yield compared to the non-treatedcontrol (Table 3). Results are similar to other studies thathave shown no reduction in cabbage yield with pre-transplant applications of dimethenamid-p at 750 and1500 g a.i./ha, another chloracetamide herbicide (Sikkemaet al., 2007). Dimethenamid-p applied post-transplantcaused no injury to cabbage in Tennessee, USA (Shamiyehet al., 2001). Other herbicides such as oxyfluorfen appliedpre-transplant and post-transplant have been reported tocause minimal injury in cabbage (Bhowmik and McGlew,1986; Gorski and Hopen, 1978; Grabowski andHopen, 1984). This is in contrast to sulfentrazone thathas the potential to cause moderate to severe crop

injury in cabbage (Shamiyeh et al., 2001; Umeda andMurrieta, 1998).

4. Conclusions

This research was initiated to evaluate s-metolachlorapplied pre-transplant incorporated, pre-transplant andpost-transplant at 800, 1600 and 2400 g a.i./ha for potentialregistration in cabbage in Ontario. There was no effect onvisual injury, marketable head number, marketable headweight and yield of cabbage at any of the s-metolachlordoses or application timings evaluated.

s-Metolachlor applied pre-transplant incorporated, pre-transplant and post-transplant at the doses evaluated hasthe potential for use in cabbage in Ontario. Registration ofs-metolachlor as a pre-transplant incorporated and pre-transplant herbicide for use in cabbage would providegrowers with an expanded timing means to controlcertain troublesome weeds such as C. esculentus andS. ptycanthum.

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