WIRESTEM MUHLY

Abstracts:

• Control of Wirestem Muhly in Herbicide Resistant Corn. Lingenfelter, D. D. and Curran, W. S. 1999. Abstr. NEWSS 53:65.
  
  
• Effect of Preplant Tillage and Nicosulfuron on Wirestem Muhly Control in Corn. D. D. Lingenfelter and W. S. Curran, 1997. Proc. NEWSS 51:15.
  
  
• Effect of Glyphosate and Several ACCase Inhibitor Herbicides on Wirestem Muhly Control. D. D. Lingenfelter and W. S. Curran, 1996. Proc. NEWSS 50:36.
  
  
• Effect of Glyphosate Application Timing on the Control of Wirestem Muhly (Muhlenbergia frondosa (Poir.) Fernald). D. D. Lingenfelter and W. S. Curran, 1997. WSSA Abstracts 37:27.
  
  
• Effectiveness of Adjuvants with Nicosulfuron and Primisulfuron for Wirestem Muhly (Muhlenbergia frondosa) Control in No-Till Corn (Zea mays). Vijay K. Nandula, William S. Curran, Gregory W. Roth, and Nathan L. Hartwig, 1995. Weed Technol. 9:525-530.

Control of Wirestem Muhly in Herbicide Resistant Corn. Lingenfelter, D. D. and Curran, W. S. 1999. Abstr. NEWSS 53:65.

Wirestem muhly (Muhlenbergia frondosa (Poir.) Fernald) is a warm season, perennial grass species that is a problem in conservation tillage systems. Effective programs are limited for managing wirestem muhly using traditional corn hybrids in conservation tillage systems. The following demonstrations were designed to evaluate wirestem muhly control using several herbicides in herbicide resistant corn (Zea mays L.) hybrids.

In 1997 and 1998, field demonstrations were conducted in central Pennsylvania in a no-till area with an established wirestem muhly population. In 1997, Poast Protected/SR corn was planted in the entire trial area in early May and followed with a burndown/PRE treatment for annual weed control. Postemergence herbicide treatments included Poast Plus (sethoxydim), Accent (nicosulfuron), and Basis Gold (nicosulfuron + rimsulfuron + atrazine) at different rates, timings, and in combinations. Appropriate adjuvants were included where necessary. A randomized complete block design (10 by 100 feet) with two replications was used in this study. In 1998, three herbicide resistant corn hybrids (Poast Protected/SR, Roundup Ready, and Liberty Link/GR) were strip-planted in the trial area during mid-May and a burndown/PRE treatment applied for annual weed control. The primary postemergence herbicide treatments included Liberty (glufosinate), Poast Plus, and Roundup Ultra (glyphosate) at different rates and timings. The primary treatments were applied in combinations with and compared to other standard corn herbicides. Appropriate adjuvants were included where necessary. A nonreplicated strip design (15 by 90 feet) was used in the demonstration. In both years, the herbicides were applied with a CO2-backpack sprayer when wirestem muhly was 10 to 12 inches tall (POST1) and 15 to 18 inches tall (POST2). Treatments were evaluated visually.

End of season results from the studies showed that in 1997, Poast Plus treatments provided 60% to 70% control with a single application and the same treatments provided 75% to 95% control in 1998. A split application of Poast Plus provided greater than 90% control of wirestem muhly. Accent provided no more than 80% control as either a single application or a split treatment. Basis Gold only slightly suppressed wirestem muhly growth (30% control). The single Liberty application provided 40% control of wirestem muhly, whereas the split treatment provided 77% control. Roundup Ultra provided excellent initial control (100%) of wirestem muhly. However, by the end-of-season, wirestem muhly control was 75% to 85%, probably due to the emergence of new shoots. Tank mixing Accent, Basis Gold, or atrazine with the primary herbicide treatments did not increase the level of wirestem muhly control. In some tank mix treatments antagonism was observed, namely, Basis Gold plus Poast Plus and Roundup Ultra plus atrazine.

In summary, these strip trials show that wirestem muhly can be more effectively managed with certain herbicides in herbicide resistant corn hybrids as compared to traditional corn herbicides. As noted in these studies and from previous research conducted at Penn State University, herbicide application timing and perhaps split treatments are necessary for effective wirestem muhly control. Herbicide resistant crops with an appropriate herbicide treatment should be an excellent alternative for managing wirestem muhly in corn in areas where tillage is not feasible.

Effect of Preplant Tillage and Nicosulfuron on Wirestem Muhly Control in Corn. D. D. Lingenfelter and W. S. Curran, 1997. Proc. NEWSS 51:15.

Wirestem muhly (Muhlenbergia frondosa (Poir.) Fernald) is a warm season, perennial grass species that is becoming a problem in conservation tillage systems. Effective programs currently do not exist for managing wirestem muhly in reduced-tillage corn. Therefore, the following research was designed to evaluate preplant tillage with and without nicosulfuron for wirestem muhly control in corn (Zea mays L.).

In 1994 and 1995, field studies were conducted in central Pennsylvania at locations with established wirestem muhly populations. Spring primary preplant tillage treatments were moldboard plow, chisel plow, heavy disk, and no-till. Secondary tillage was performed where necessary to obtain an appropriate seedbed. Corn was planted in mid to late May and followed with a burndown/PRE treatment for annual weed control. Nicosulfuron at 0.031 lb ai/A plus 0.25% v/v nonionic surfactant was applied postemergence when wirestem muhly was 12 to 18 inches tall and corn was less than 24 inches tall (V4-V5 stage). A split-plot design with three replications was used in this study. The herbicide was applied with a CO₂-backpack sprayer that delivered 20 gpa.

End of season results from the study showed that nicosulfuron in combination with moldboard plow, chisel plow, or heavy disk treatments provided greater than 92% control of wirestem muhly. Moldboard plow, chisel plow, and disk without a POST treatment were less effective, only providing 45 to 60% control. The year following tillage and herbicide application, wirestem muhly control ranged from 89 to 98% for all tillage systems that included nicosulfuron. Tillage treatments without the POST herbicide provided less than 45% control. In general, control in treatments that included nicosulfuron was better than for treatments without the herbicide.

In 1994, corn grain yield was 80 bu/A for no-till without nicosulfuron and 90 bu/A with the herbicide treatment. All other treatments, except chisel plow and no POST herbicide, yielded 100 to 117 bu/A. Corn yields from the 1995 season, a drought year, ranged from 51 to 75 bu/A. None of the combination treatments differed.

In summary, these results show that wirestem muhly can be more effectively managed when a combination of control measures are used. In general, spring primary tillage followed by an application of nicosulfuron was more effective than tillage or herbicide alone. Corn yield was not greatly affected by the presence of wirestem muhly, although competitive indices for wirestem muhly in corn have not yet been studied or established. For areas where tillage is not feasible, nicosulfuron will suppress the wirestem muhly until additional control measures can be accomplished in other crops (e.g., soybeans).

Effect of Glyphosate and Several ACCase Inhibitor Herbicides on Wirestem Muhly Control. D. D. Lingenfelter and W. S. Curran, 1996. Proc. NEWSS 50:36.

Wirestem muhly (Muhlenbergia frondosa (Poir.) Fernald) is a warm season, perennial grass species that is becoming a problem in conservation tillage systems. Effective programs currently do not exist for managing wirestem muhly in reduced-tillage corn. The following research was designed to evaluate glyphosate and several ACCase inhibitor herbicides for wirestem muhly control in soybeans. In addition, the effect of glyphosate application timing on the control of wirestem muhly was evaluated in a fallow period.

In 1994 and 1995, field studies were conducted in central Pennsylvania at locations with established wirestem muhly populations. Following a burndown/PRE treatment for annual weed control, transgenic (glyphosate-tolerant) soybeans (Glycine max) were planted in mid to late May. Glyphosate, fluazifop, quizalofop, sethoxydim, and clethodim, plus appropriate adjuvants, were applied postemergence at two rates and two application timings. Glyphosate was applied at 0.5 and 1.0 lb ai/A and the ACCase inhibitor herbicides were applied at 0.67X and 1X the manufacturer's recommended application rate. Herbicides were applied 4 and 6 WAP when wirestem muhly was 10 to 12" and 18 to 20" tall, respectively. In the fallow period study, glyphosate, plus 0.25% (v/v) nonionic surfactant, was applied at 0.5 and 1.0 lb ai/A at two to three week intervals from mid May through mid October (or first killing frost). A randomized complete block design with four replications was used for all studies. Herbicides were applied with a CO₂-backpack sprayer that delivered 10 gpa.

End of season results from the soybean study show that both rates of glyphosate provided less than 80% control of wirestem muhly with the early application timing and greater than 95% control from the later application. Fluazifop and clethodim gave similar control (70 to 80%) over both rates and application timings. Sethoxydim and quizalofop were less effective at controlling wirestem muhly, providing only 50 to 65% control for both rates and timings.

In the fallow period study, the end of season ratings revealed that glyphosate provided 90 to 100% control of wirestem muhly from applications made in mid June to late September. Preliminary results show that glyphosate provided 65 to 85% control of wirestem muhly the year following treatments made between mid June and mid August. Earlier or later application timings always provided less than 65% control.

In summary, these results show that glyphosate, fluazifop, and clethodim provided season long control of wirestem muhly in soybeans. Quizalofop and sethoxydim were not as effective at wirestem muhly control. With the introduction of glyphosate-tolerant soybean varieties, timely postemergence applications of glyphosate will be more feasible, allowing for longer term control of wirestem muhly. Greenhouse studies are currently underway to complement the field trials.

Effect of Glyphosate Application Timing on the Control of Wirestem Muhly (Muhlenbergia frondosa (Poir.) Fernald). D. D. Lingenfelter and W. S. Curran, 1997. WSSA Abstracts 37:27.

Field research was conducted in 1994 to 1995 to identify optimum glyphosate application timing for long-term control of wirestem muhly. Research was conducted in established infestations of wirestem muhly. No crop was planted in the experimental area during the study. Glyphosate plus 0.25% (v/v) nonionic surfactant was applied at 0.56 and 1.12 kg ai ha^-1 at 14 to 21 day intervals from mid-May through mid-October (or first killing frost). Herbicides were applied with a CO₂-backpack sprayer that delivered 94 L ha^-1. A RCB design with four replications was used for the experiment. End of season ratings in 1994 and 1995 revealed that glyphosate provided 90 to 100% control of wirestem muhly from applications made in mid-June to late-September. The year following application, glyphosate provided 65 to 85% control of wirestem muhly from applications made between mid-June to mid-August 1994. The year after application in 1995, 75 to 98% control of wirestem muhly was achieved with mid-June to late-September application. Applications earlier than mid-June or after September always provided less than 65% control. In summary, these results show that glyphosate can provide excellent season-long and long-term control of wirestem muhly when applied during the summer months. Early season burndown prior to crop establishment or fall applications of glyphosate do not provide effective control of wirestem muhly. With the introduction of glyphosate-tolerant crop varieties, timely postemergence applications of glyphosate will be more feasible, allowing for better management of wirestem muhly.

Effectiveness of Nicosulfuron and Primisulfuron on Wirestem Muhly (Muhlenbergia frondosa) in No-Till Corn (Zea mays). Vijay K. Nandula, William S. Curran, Gregory W. Roth, and Nathan L. Hartwig, 1995. Weed Technol. 9:331-338.

Field experiments were conducted in 1992 and 1993 to evaluate wirestem muhly control in no-till corn with application of glyphosate, nicosulfuron, and primisulfuron. Glyphosate was applied preplant at 1.1 kg ai/ha, while nicosulfuron and primisulfuron were applied from 0.5 to 2X the normal rate and at four postemergence timings that included a split application. Similar experiments were conducted with wirestem muhly grown from rhizomes and seed in the greenhouse. Glyphosate was the most effective herbicide in the greenhouse, providing at least 96% control. However, preplant application of glyphosate in the field was ineffective in controlling wirestem muhly. Nicosulfuron and primisulfuron did not fully control wirestem muhly in the greenhouse or in the field. Nicosulfuron was generally better, but only slightly than, primisulfuron and although marginally effective, earlier applications or split treatments provided the most early season suppression of wirestem muhly. Control with split application timings was more uniform over a 12 week period than single applications and late postemergence applications were often too slow acting to impact wirestem muhly growth. Although neither nicosulfuron or primisulfuron provide more than suppression of wirestem muhly, both can provide short-term control of this weed where other alternatives do not exist.

Effectiveness of Adjuvants with Nicosulfuron and Primisulfuron for Wirestem Muhly (Muhlenbergia frondosa) Control in No-Till Corn (Zea mays). Vijay K. Nandula, William S. Curran, Gregory W. Roth, and Nathan L. Hartwig, 1995. Weed Technol. 9:525-530.

Greenhouse and field experiments were conducted to evaluate the effectiveness of nicosulfuron and primisulfuron with different adjuvants on wirestem muhly control. The adjuvants evaluated with the two herbicides included a nonionic surfactant, crop-oil concentrate, crop-oil concentrate plus urea-ammonium nitrate, methylated vegetable-oil concentrate, and organosilicone methylated vegetable-oil concentrate. In the greenhouse, nicosulfuron and primisulfuron performance was similar, although small differences occurred between adjuvants and herbicides. In the field, changing adjuvant affected nicosulfuron performance more than primisulfuron and in general, greater control was achieved with nicosulfuron than with primisulfuron. Among adjuvants, methylated vegetable-oil concentrate provided greater wirestem muhly control with nicosulfuron and sometimes primisulfuron compared to the others, while the nonionic surfactant was the least effective with both herbicides. Regardless of adjuvant, none of the field-applied treatments controlled wirestem muhly much beyond the 12 week evaluation period.