© 2004 Plant Management Network.
Redstem Filaree Control in Sugarbeets with Micro-rate Herbicide Treatments
Abdel O. Mesbah, Research Scientist, Plant Science Department, Powell Research and Extension Center, University of Wyoming, Powell 82435; Stephen D. Miller, Professor, Plant Science Department, University of Wyoming, Laramie 82071; and W. Bart Stevens, Assistant Professor, Department of Renewable Resources, Powell Research and Extension Center, University of Wyoming, Powell 82435
Corresponding author: Abdel O. Mesbah. email@example.com
Mesbah, A. O., Miller, S. D., and Stevens, W. B. 2004. Redstem filaree control in sugarbeets with micro-rate herbicide treatments. Online. Crop Management doi:10.1094/CM-2004-0826-01-RS.
Field experiments were conducted at the University of Wyoming Powell Research and Extension Center to evaluate redstem filaree control and sugarbeet response to several herbicide treatments. Preplant herbicides used were ethofumesate and pyrazon applied alone or in combination. Postemergence herbicides included desmedipham-phenmedipham-ethofumesate plus triflusulfuron plus clopyralid at various application rates and timings. A standard postemergence treatment was compared with a micro-rate system, which included 1.5% methylated seed oil. Redstem filaree control was influenced by number and time of applications. Treatments applied at cotyledon stage provided better control than those applied at 2-leaf sugarbeet stage. Redstem filaree control increased as the number of applications increased. With or without preplant herbicides, four sequential applications using micro-rate provided more than 90% redstem filaree control. Micro-rate treatments with methylated seed oil adjuvant were significantly superior to standard treatments in controlling redstem filaree. There was no significant difference in redstem filaree control between treatments containing preplant herbicides and those without, suggesting that preplant herbicides may not be necessary. Preplant herbicides followed by standard rate postemergence treatments showed more injury than those followed by micro-rate treatments. Sugarbeet root yield was higher in treated plots than in the untreated check and was closely related to both redstem filaree control and sugarbeet injury. Sugar content was not affected by any of the herbicide treatments. With or without preplant herbicides, four sequential micro-rate applications provided significantly higher yields than standard postemergence treatments.
Redstem filaree (Erodium cicutarium L.) is becoming a serious weed problem for sugarbeet (Beta vulgaris L.) growers in northern Wyoming and southern Montana. This weed species originated in the Mediterranean region of Europe and has spread to many areas of the world including Africa (14), Australia (12), and North and South America (6,7,10). Redstem filaree, a winter annual or biennial broadleaf, is a prolific seed producer (3) and can quickly develop into dense infestations under non-competitive conditions. Blackshaw (2) reported that under controlled environmental conditions, redstem filaree seeds germinated at soil temperatures of 5 to 20°C and produced optimal vegetative growth at 15 to 20°C.
Little information is available on redstem filaree’s ability to compete with row crops. Studies have shown that redstem filaree has the potential to compete and cause major economic losses in perennial pasture and forage crops such as alfalfa (Medicago sativa L.) (6,9) and in annual cereals and oilseed crops (4). In a zero-tillage cropping system study, Blackshaw et al. (5) found that an increase in wheat (Triticum aestivum L.) seeding rate from 50 to 300 kg/ha reduced redstem filaree biomass and seed production by 53 to 95%. Limited data are available on the competitive effect and control of redstem filaree in sugarbeets (8).
This study was conducted to determine (a) the effect of preplant and postemergence herbicides on redstem filaree control, and (b) the effect of herbicide rate, number of applications, and timing of applications required to control redstem filaree without reducing sugarbeet root yield.
Field Experiment Design and Implementation
Field experiments were conducted in 2001 and 2002 at the University of Wyoming Research and Extension Center, Powell, WY on a Garland clay loam soil (fine, mixed Mesic, Typic Haplargid) with pH 7.7 and 1.4% organic matter. Soil fertility status was determined by soil test. N and P were applied according to University of Wyoming recommendations (N at 200 to 220 lb/acre and P2O5 at 90 to 105 lb/acre). Fields were prepared in the fall by moldboard plowing and roller harrowing and bedded in the spring. The tops of the beds were leveled to provide a uniform seedbed for planting. Sugarbeet (cv. Geyser) seeds were planted at a depth of one inch on April 19, 2001 and April 28, 2002 in rows spaced 22 inches apart at a rate of three seeds per foot. Redstem filaree seeds were broadcast with a cyclone seeder prior to sugarbeet planting at a rate of 10 seeds per ft2. Aldicarb [2-methyl-2(methylthio) propionaldehyde O(methylcarbamoyl) oxine] was applied for insect control at 12 lb/acre and incorporated to a depth of 1 to1.5 inches.
All treatments (12 preplant followed by postemergence treatments, 6 postemergence without preplant treatments, and an untreated check) were arranged in a randomized complete block design with three replications. Preplant herbicides consisted of either no herbicide (control), ethofumesate, pyrazon, or the combination ethofumesate+pyrazon applied at 1.5, 1.5, and 1+1 lb ai/acre, respectively. A spray volume of 20 gal/acre at 40 psi through 8002 nozzles was used, and herbicides were incorporated to a depth of 1 to 1.5 inches with a rotary power incorporator during the planting operation. Postemergence treatments consisted of the combination desmedipham-phenmedipham-ethofumesate (DPE) + triflusulfuron (Trif) + clopyralid (Clop) applied broadcast at both standard and micro-rates (Table 1) using a CO2 pressurized knapsack sprayer delivering 20 gal/acre at 40 psi through 8002 nozzles. Standard-rate refers to the label rate. Micro-rate is a system developed by Alan Dexter (1), North Dakota State University/University of Minnesota Extension Sugarbeet Specialist. This system consists of reducing the label rate by 66 to 75% and adding methylated seed oil (MSO) at 1.5 % by volume. Micro-rate system requires three to five applications with 5 to 7 day interval between applications. Standard-rate treatments consisted of either two or three sequential applications with the first occurring when sugarbeets were either at cotyledon or two-leaf stage, while micro-rate treatments consisted of either three or four sequential applications starting when sugarbeets were in cotyledon stage. The interval between applications was 7 days for both standard and micro-rate treatments. The untreated check was hand-weeded twice to remove weeds other than redstem filaree, when sugarbeet was at 2 and again at 6 leaf stage.
Table 1. Postemergence herbicide costs and application rates for each application of the standard and micro rate treatments. Application costs were estimated to be $4.00/acre per application.
Each plot consisted of six sugarbeet rows spaced 22 inches apart and 30 ft in length. Redstem filaree plant counts were taken from a 6-inch by 10-ft area from the two center rows in each plot 4 weeks after the last herbicide application. These counts were converted to percent control based on the density in the untreated plots. Sugarbeet injury was visually evaluated 2 weeks after the last application. Sugarbeeta were defoliated mechanically and harvested using a mechanical, single-row harvester October 11, 2001 and October 7, 2002. Sugarbeet roots from the center row of each plot were lifted and weighed. The total sugarbeet weight from each plot was used to calculate root yield. A sample of 10 sugarbeet roots was randomly collected from each plot to determine sucrose content.
Sugarbeet injury, root yield, sucrose content, and percent redstem filaree control data were analyzed using standard analysis of variance procedures (11). When significant differences were detected among treatments, Fisher’s protected Least Significant Difference (LSD) at a 5% probability level was calculated and used as a mean separation technique. Orthogonal contrasts were performed to compare standard to micro-rate and treatments containing preplant to those without.
An economic analysis was performed to determine the profitability of each treatment. Gross income was determined by multiplying sugarbeet root yield by the average price ($39.4/ton) received by the sugarbeet growers in the Big Horn Basin, Wyoming for 2001 and 2002 (13). Costs used in the analysis included herbicide and custom application costs for treated plots and hand labor cost for untreated plots. Ethofumesate and pyrazon costs were $40.5 and 37.5 /acre, respectively. Postemergence herbicide costs per acre are presented in Table 1. The cost of each application was $4/acre. These costs reflect the average price quoted by two major custom applicators in the area. The average hand labor cost paid by sugarbeet growers in the Big Horn Basin was $69/acre. Herbicide costs were subtracted from gross income to calculate the net income (considering only the herbicide costs) for each treatment.
Redstem Filaree Control and Sugarbeet Response
There was no significant year by treatment interaction for redstem filaree control, yield, injury, or sugar content; therefore, data were combined over years (Table 2).
Table 2. Redstem filaree control, sugarbeet response, and net income from several herbicide treatments, Powell, WY (ave. 2001–2002 data). Net income calculation considers only herbicide costs, application costs, and value of yield, not total production or fixed costs.
x Abbreviations: Pyra = Pyrazon; Etho = Ethofumesate; None = No preplant treatments.
y Abbreviations: DPE = commercial premix of desmedipham, phenmedipham and ethofumesate; Trif = triflusulfuron; Clop = clopyralid; Stand = standard rate; Micro = micro rate; Stages: Co = cotyledon stage of sugarbeet; 2, 4, and 6 = Sugarbeet leaf number at time of application.
z Contrasts test: Asterisk (*) denotes significance at P < 0.05; NS = not significant.
Redstem filaree control. Redstem filaree density following herbicide treatments was significantly lower in treated plots than in the weedy check (Table 2). Redstem filaree control ranged from 55 to 96% and was influenced by number and time of applications. With or without preplant herbicides, redstem filaree control with standard- and micro-rate treatments increased as the number of postemergence applications increased from two to three and three to four, respectively (Table 2). Micro-rate treatments with methylated seed oil adjuvant were significantly superior to standard treatments in controlling redstem filaree. The best control (> 90%) was achieved with the treatments containing four sequential micro-rate applications. Postemergence treatments applied at cotyledon stage provided greater redstem filaree control than those applied at two leaf stage. The poorest redstem filaree control (55 and 67%) was provided by two and three sequential applications starting at two sugarbeet leaf stage, respectively.
Sugarbeet response. Sugarbeet injury ranged from 0 to 9%. Pyrazon preplant followed by three sequential applications using standard rate caused the highest injury (9%). Sugarbeet root yields were higher in treated plots than in the untreated check. Sugarbeet root yield in the treated plots ranged from 19.7 to 26.6 tons/acre and was influenced by number and time of applications. With or without preplant treatments, four sequential applications using micro-rate provided more than a 7% yield increase, compared to the untreated check. The lowest yields (19.7 and 20.8 tons/acre) were provided by two and three postemergence applications starting at two sugarbeet leaf stage, respectively. In general, root yields appeared to be related to both redstem filaree control and sugarbeet injury. No significant difference in sucrose content was detected between the herbicide treatments and the untreated check.
Net income. Net income ranged from approximately US$645 to US$960/acre, and was influenced by sugarbeet root yield and herbicide costs. Three sequential standard rate applications starting at 2 leaf sugarbeet stage produced the lowest net income, while four sequential micro rate applications produced the highest net income.
The results of this study show that redstem filaree control is influenced by the timing and number of applications. Redstem filaree is more sensitive to herbicide injury at the cotyledon stage than at the two-leaf stage. Preplant treatments combined with postemergence treatments generally were not superior to postemergence treatments alone; thus if post-emergence treatments are anticipated, preplant treatments may not be necessary. This study suggests that multiple "micro" treatments were most effective at controlling redstem filaree, with or without preplant herbicides. To achieve maximum net income, four sequential micro-rate applications without preplant herbicides are recommended.
The authors express their appreciation to the Western Sugar Co.-Grower Joint Research Committee for funding this research and performing sugarbeet sucrose analyses. Special thanks to staff at the University of Wyoming Powell Research and Extension Center for their assistance.
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