Abstract: Experiment was conducted in 2013 to evaluate various herbicide treatment regimes for POST yellow nutsedge control. Evaluated herbicides included metsulfuron-methyl+sulfosulfuron, Oxadiazon, Clothedim, Sicloxidim, Nicosulfuron+Rimsulfuron and untreated check. Evaluated treatments did not cause objectionable bermudagrass injury at any time. The highest and the lowest dry weight of turfgrass was achieved in Oxadiazon (211 g m–2) and untreated plots (130 g m–2), respectively. The results of this study indicate that satisfactory control of yellow nutsedge (>90%) obtained by post-emergence application of oxadiazon, clothedim or sicloxidim at the first time and repeat applications will not be required. Further, our results indicate that efforts to enhance yellow nutsedge control with metsulfuron-methyl+sulfosulfuron and nicosulfuron+rimsulfuron timings and repeat applications were inconsistent. These data confirm that the lower bermudagrass phytotoxicity was achieved with the sicloxidim treatment.
INTRODUCTION
Yellow nutsedge, is common perennial sedge in turfgrass systems and grow best in above-normal soil moisture (Bendixen and Nandihalli, 1987; Bryson et al., 1997; McCarty et al., 2008; McElroy et al., 2005a). Yellow nutsedge is more commonly observed in higher mowing heights (Summerlin, 1997). This species exhibits prolific vegetative growth and produces rhizomes and also produce basal bulbs, seed and tubers (McCarty et al., 2008; Stoller et al., 1972; Stoller and Sweet, 1987). Yellow nutsedge has been described as one of the world’s worst weeds (Stoller and Sweet, 1987). Yellow nutsedge is able to survive cooler climates and is more widely distributed than purple nutsedge (Martinez-Ochoa et al., 2004; McCarty et al., 2008; Stoller and Sweet, 1987). This may be because of its ability to increase tuber starch, sugar and lipid content in response to temperature (Bendixen and Nandihalli, 1987). Unlike purple nutsedge, yellow nutsedge does not produce tuber chains. Yellow nutsedge is cultivated for edible tubers in southern Europe and Africa (Wills, 1987). The incidence of sedge species has increased in recent years in turfgrass systems likely due in part to changes in herbicide programs (Yelverton, 1996). Traditionally, chemical control is a effective method in weed control but there is not a selective herbicide for grassy control. Most herbicides used for weed control in turf areas are for control of broad leafed such as; 2,4-D, 2,4-DP, MCPP, MCPA, dicamba, triclopyr, carfentrazone, sulfentrazone, quinclorac (Busey, 2003). Few herbicide options are available for control of weed grasses in turf areas. The most common herbicide choice is a general purpose mixture comprised of two or three of the following individual herbicides or active ingredients; 2,4-D, MCPP (mecoprop); and dicamba (Emmons, 2008).
Sulfosulfuron is a selective herbicide for control of annual and perennial grass and broadleaf weeds in highly managed turf sites (Senseman, 2007; Watschke et al., 2013). Select warm and cool-season turfgrasses have exhibited tolerance to sulfosulfuron up to 105 g ha–1 (Anonymous, 2010c; Lycan and Hart, 2004; Willis et al., 2007). Zabihollahi et al. (2008) was studied postemergence herbicides efficacy on bermudagrass (Cynodon dactylon) control in turf mixture of landscape and reported that Fenoxaprop-p-ethyl at 60 g ai ha–1 is the best herbicide for bermudagrass control. It was reported that among dual-purpose herbicides, sulfosulfuron (EC75%) 27 g ha–1 and nicosulfuron ((SG 4%) l.5 g ha–1 by having 76.36 and 56.95 biomass (% of untreated control) had the most and the least effect on turf species (Norouzi et al., 2013). Oxadiazon or the mixture of acetochlor and oxadiazon had good control of weeds in lawns and turf. Acetochlor had largest negative effects on growth of lawns and turf (Wang et al., 2003). Turfgrass and smooth crabgrass response to flazasulfuron, foramsulfuron, metsulfuron, rimsulfuron, sulfosulfuron and trifloxysulfuron-sodium, applied 1 and 3 weeks after and before seeding was studied by Willis et al. (2007). They were reported that herbicides applied 3 Weeks After Seeding (WAS) generally more injurious than when applied 1 WAS. Foramsulfuron, metsulfuron and sulfosulfuron are safe to apply 1 and 3 WAS, causing no reduction in turf cover.
Nicosulfuron is a postemergence sulfonylurea herbicide labeled for use in corn (Zea mays L.) and controls many difficult to control grassy weeds and some broadleaf weeds at rates of 17.5-70 g ai ha–1 (Bhowmik et al., 1992). A single application of Nicosulfuron controlled over 90% of quackgrass (Elythigia repens (L.) Gould) five Weeks After Treatment (WAT) and provided greater than 80% control one year later (Bhowmik et al., 1992). Metsulfuron controls several broadleaf weeds in bermudagrass (Anonymous, 2010b). Kelly and Coats (2000) reported that metsulfuron alone controlled virginia button weed as effectively as, 2,4-D and combining the two herbicides was not advantageous, if metsulfuron was applied at 32 g ha–1 or higher. Bradley et al. (2004) reported that metsulfuron controlled broadleaf plantain (Plantago major L.), buckhorn plantain (Plantago lanceolata L.) and wild carrot (Daucus carota L.) 70-90%. When, applied alone or in combination with 2,4-D, metsulfuron reduced herbaceous broadleaf plant ground cover at several locations (Meyer and Bovey, 1990). Metsulfuron applied alone is not injurious to bermudagrass (Anonymous, 2010a).
As above mentioned herbicide efficacy may be governed by the effect of herbicide placement and site of uptake and action. Effects of selective herbicide placement on sedge control have been previously reported for certain herbicides (McElroy et al., 2003; Nandihalli and Bendixen, 1988; Reddy and Bendixen, 1988). However, information regarding the response of sedge species to currently available herbicides is limited. The objective of this research was to determine the efficacy of some postemergence herbicides on yellow nutsedge growth, determine the optimal timing for sequential applications and determine the safety of these herbicides on bermudagrass turf.
MATERIALS AND METHODS
Field experiments were initiated during the autumn of 2013 and 2014 at Ahwaz in Khoozestan Province, Iran (32°3’N, 48°50’E). The climate is arid and semi-arid with a mean annual rainfall of 198.4 mm and the average of annual minimum and maximum 9.5 and 48.3°C, respectively. The soil was a clay loam texture, pH of 7.2, soil electrical conductivity was 1.2 ds m–1 and 0.3% organic matter content. The available phosphorous and potassium were 10.2 and 150 ppm, respectively. Research was performed on established yellow nutsedge infestations present in a common bermudagrass rough maintained at a height of 5.4 cm. Plots measured 1.5 by 1.5 m and were arranged in a randomized complete block design with four replications. Yellow nutsedge cover (50-90%) within each plot was determined at the time of initial herbicide application through grid counts using a 0.3 m2 grid (25 intersecting points) tossed into each plot. All experimental areas were mowed 24 h before herbicide application and once 10 days thereafter. There was no rain or irrigation during the 24 h period after herbicide treatment.
Herbicide treatments included 3 times spraying with metsulfuron-methyl+sulfosulfuron (Total® WG80%) 40 g ha–1, Oxadiazon (Ronstar® EC12%) 2 L ha–1, Clothedim (Select super® EC 12%) 1 L ha–1, Sicloxidim (Focus® EC10%) 2 L ha–1, Nicosulfuron+Rimsulfuron (Ultima® WG75%) 175 g ha–1 and untreated check.
Treatments were initiated on October 5, 2014 with sequential applications made 4 and 8 WAIT (weeks after initial treatment). Treatments were applied using a CO2-pressurized backpack sprayer equipped with two XR8003VS flat-fan extended-range spray tips (Teejet, Spraying Systems Co., North Ave. and Schmale Rd., Wheaton, IL 60129) and calibrated to deliver 304 L ha–1 at 276 kPa.
Data collected included bermudagrass phytotoxicity and yellow nutsedge control based on grid counts was evaluated at three times throughout duration of the experiment. Visual assessments of plant and weed injury were made 10 days after herbicide application using a scale of European System of Weed Control and Crop injury Evaluation (Burrill et al., 1976) with some modified that scale of 0-100% was used, where 0 = no injury, >70% = acceptable control and 100 = completely killed (Table 1) (Uddin et al., 2014).
Dry weight of turf grass and yellow nutsedge were recorded by oven-dried at 70°C for 72 h at three sampling stages. For quantitative analysis, Weed Control Efficacy (WCE) was determined by percent weed control in the treated plot in comparison with that of untreated plot:
where, a is the weed biomass in control treatment (weed free) and b is the weed biomass in sprayed treatment. Finally, all the data were subjected to statistical analysis using SAS computer software after arcsine transformation of percent weed control data and LSD test was performed at the 5% probability level for mean comparison (SAS).
RESULTS AND DISCUSSION
Bermudagrass phytotoxicity exceeded 9% on observation of 8WAIT in all herbicide treatments but all bermudagrass recovered within 7 d of herbicide application. At 8 WAIT, the maximum turf injury was observed at Ultima (175 g ha–1) by 19.34% with no significant difference with Total (40 g L–1), followed by Ronstar (2 L ha–1) and Select super (1 L ha–1). The least damage by 9.45% observed in Focus (2 L ha–1) herbicide. Norouzi et al. (2013) reported that Poa had high resistance to Acetyl coenzyme A carboxylase (ACCase) inhibitor herbicides. The same result was reported by Zabihollahi et al. (2008).
| Table 1: | Treatments and application dates |
| Table 2: | Injury rating scale of weed and turf |
| Table 3: | Control of yellow nutsedge present in bermudagrass turf and bermudagrass phytotoxicity at third application time |
| Means within a column followed by the same lowercase letter are not significantly different at p≤0.05 according to Fisher’s protected LSD test. IT: Initial treatment, WAIT: Weeks after initial treatment | |
McElroy et al. (2005b) found that MSMA, clopyralid and quinclorac did not injure seedling bermudagrass, while diclofop, metsulfuron, 2,4-D and dicamba injured seedling bermudagrass.
Herbicide treatment main effects were observed for yellow nutsedge control at IT, 4 and 8 WAIT (Table 2). Ronstar and Focus (2 L ha–1) 4 WAIT, Ronstar, Focus and Select super exhibited 90-99% control 4 and 8 WAIT (Table 3). Felix and Boydston (2010) observed similar control of yellow nutsedge (92-99%) with imazosulfuron applied PRE and POST at 0.34-0.56 kg ai ha–1 42 DAIT. Yelverton et al. (2003) reported similar purple nutsedge control (>85%) 4 WAIT with applications of flazasulfuron at 0.025-0.1 kg ai ha–1.
Four and Eight weeks (4 and 8 WAIT), sequential application of Ronstar (2 L ha–1) controlled yellow nutsedge 99 and 95%, whereas similar control (90-91%) was observed with a single application of Ronstar and Focus (2 L ha–1) followed by Select super 4 and 8 WAIT (Table 3). Baumann et al. (2004) observed similar control (80-85%) 104 DAT with sequential applications of sulfosulfuron at 0.05-0.1 kg ai ha–1 and halosulfuron at 0.07 kg ai ha–1. Season-long yellow nutsedge control (90-95%) has been observed with sequential applications of sulfosulfuron at 0.078 kg ai ha–1 (Brecke et al., 2007). Hinton and Yelverton (2003) observed greater control (>90%) 12 WAIT with sequential applications of trifloxysulfuron at 0.03 kg ai ha–1. Application 2 or 3 times for sequential Ronstar and Focus rather than 1 time, increased yellow nutsedge control. However, control with these treatments was not statistically different from control with a single application (Table 3). Sequential applications made several weeks later may allow for increased herbicide uptake due to the presence of more leaf tissue after regrowth. Yellow nutsedge produces rhizomes and also produce basal bulbs and tubers used to store carbohydrates for emergence and growth in subsequent years. Effective yellow nutsedge control is likely limited by absorption and translocation of applied herbicides. Leys and Slife (1988) reported 58% of applied 14C metsulfuron was readily absorbed by wild garlic (Allium vineale L.) 144 h after application and 16% of that absorbed material translocated out of the treated leaf. Troxler et al. (2003) observed 53% or less of applied 14C-trifloxysulfuron was absorbed by yellow nutsedge (Cyperus esculentus L.) and purple nutsedge (C. rotundus L.) 96 h after treatment.
| Table 4: | Dry weight of yellow nutsedge and turfgrass influenced by different post-emergence herbicides |
| Means within a column followed by the same lowercase letter are not significantly different at p≤0.05 according to Fisher’s protected LSD test | |
Unlike turfgrass, the least yellow nutsedge control was observed in Ultima (75 g ha–1) followed by Total (40 g L–1) at all application (Table 3). For herbicides inhibiting acetolactate synthase (ALS), absorption and translocation within the plant determines whole plant activity (Shaner and Singh, 1997). Because branched chain amino acid pathways are most active in meristematic regions (Shaner and Singh, 1997), ALS herbicide translocation to rhizomes is imperative for acceptable control or viability reduction. A sequential application of Total herbicide applied at IT provided 61% yellow nutsedge control whereas sequential applications applied 4 or 8 WAIT provided approximately 6-14% less control. Similarly, in Ultima herbicide, a sequential application applied at IT provided 44% yellow nutsedge control, but when sequential treatments were applied 4 or 8 WAIT, control was reduced to 5-13%. Increased control at IT may have been due to allowing sedge species to grow suitably, whereas the repeat application, 4 and 8WAIT may not be adequate to observe regrowth from previous application.
Dry weight of turfgrass and yellow nutsedge: Based on our results, herbicides type had a significant effects on dry weight of turfgrass. The maximum dry weight of turfgrass was achieved in Ronstar treatment (211 g m–2) and the lowest dry weight (130-144 g m–2) found in untreated accompanied with Ultima treatments. No significant difference was observed among Ronstar, Select super and Focus on turfgrass dry weight (Table 4). Dry weight of yellow nutsedge was significantly inhibited by all treatments. Untreated plot had the highest dry weight at all application time and the lowest dry weight found in Ronstar treatment. However there was no significant difference found among Ronstar, Select super and Focus treatments on yellow nutsedge dry weight at all sequential application (Table 4).
CONCLUSION
This study indicates Ronstar, Focus or Select super can provide acceptable yellow nutsedge control in turf environments including bermudagrass, although repeat applications will not be required. Further, our results indicate that efforts to enhance yellow nutsedge control with Total and Ultima timings and repeat applications were inconsistent. These data confirm that the lower bermudagrass phytotoxicity was achieved with the Focus treatment.