QUACKGRASS

Abstracts:

• Effectiveness of Herbicides and Tillage on Quackgrass (Elytrigia repens) Control in Corn (Zea mays). William S. Curran, Edward L. Werner, and Nathan L. Hartwig, 1994. Weed Technol. 2:324-330.
  
  
• The Effect of Tillage and Herbicide on Quackgrass Control in Corn. E.L. Werner and W.S. Curran, 1993. Proc. NEWSS 47:33.
  
  
• The Future of Quackgrass (Eritrigia repens) Control in Corn. W. S. Curran and N. L. Hartwig, 1992. Proc. NEWSS 46:43.

Postemergence applications of nicosulfuron and primisulfuron were compared to preplant glyphosate and atrazine plus simazine for quackgrass control in reduced tillage and no-till corn. The level of quackgrass control was reduced by no-till practices. At six weeks after planting, glyphosate and atrazine plus simazine were most effective in controlling quackgrass. Quackgrass biomass 12 weeks after planting indicated that the performance of the herbicides were generally similar, although primisulfuron was less effective in no-till. One year after corn planting, levels of quackgrass control in the tilled plots were the same or better than in the no-till treatments. Atrazine plus simazine was the most effective herbicide treatment over tillage systems, while primisulfuron was the least effective.

The Effect of Tillage and Herbicide on Quackgrass Control in Corn. E.L. Werner and W.S. Curran, 1993. Proc. NEWSS 47:33.

Since 1988 nicosulfuron and primisulfuron have been evaluated for quackgrass (Elytrigia repens (L.) Nevski) control at Penn State University. Initial research examined preplant treatments of the two herbicides in no-till corn. Preplant applications can provide good quackgrass control, but corn injury proved to be a concern.

Quackgrass control research at Penn State now focuses on single and split postemergence applications of nicosulfuron and primisulfuron in no-till and reduced-till corn. These treatments were compared to early preplant glyphosate treatments or an early preplant treatment of atrazine followed by a preemergence treatment of simazine. All herbicides were compared in no-till and reduced tillage systems. The tillage treatments were performed with a tandem disk followed by a finishing disk 10 days after glyphosate application. Alachlor and cyanazine were each applied at 2 lb a.i./A plus 2,4-D at 0.5 lb a.i./A preemergence over the entire study.

In 1991, quackgrass control in corn was significantly affected by both tillage and herbicide. Compared to reduced-till, the level of quackgrass control was less in no-till. Early season evaluations indicated that glyphosate and atrazine + simazine were more effective at suppressing quackgrass especially under no-till conditions. The 0.5 lb a.i./A rate of glyphosate was less effective than the 1.0 lb a.i./A rate, especially in no-till. Quackgrass biomass taken early season was significantly higher in the nicosulfuron and primisulfuron plots as compared to the glyphosate and atrazine + simazine plots, especially in no-till. Biomass samples taken mid-season indicated that quackgrass control from all herbicide treatments was similar, although samples taken from the primisulfuron treated plots were slightly higher. Split applications of both postemergence products were superior to either the single high or low rate and nicosulfuron was slightly better than primisulfuron, especially in no-till. Corn yields in no-till were significantly less than reduced-till. Control with all herbicides was adequate enough to overcome any reduction in yield.

Similar results were seen in 1992, however, the effect of tillage was more variable. In general, quackgrass control was the same or superior in the tilled plots compared to the no-till plots. As in 1991, glyphosate and atrazine + simazine provided best control early season, but by late season, levels of control were similar for the four different herbicides. The rate of glyphosate was less important in 1992, with both the 0.5 lb a.i./A rate and 1.0 lb a.i./A rate providing good control, especially in the reduced-till plots. Nicosulfuron was once again superior to primisulfuron, especially in the no-till plots and the split and full labeled rate applications were once again better than the reduced rate.

Atrazine + simazine is a high residual program that although is effective, carries some environmental and management limitations. Even at the 0.5 lb a.i./A rate glyphosate was an adequate treatment. In 1991, there was a significant difference between the 1.0 lb a.i./A rate and 0.5 lb a.i./A rate of glyphosate probably caused by drought stress brought on by an overall drier than normal season. In a year of adequate moisture as in 1992, the two rates are comparable. Tillage following application did not enhance the level of control. Both nicosulfuron and primisulfuron performance were greater in reduced-till than no-till. Split applications in general were better than any one full or reduced rate. Nicosulfuron appeared more active than primisulfuron on quackgrass, especially in no-till or when applied at reduced rates.

The Future of Quackgrass (Eritrigia repens) Control in Corn. W. S. Curran and N. L. Hartwig, 1992. Proc. NEWSS 46:43.

Prior to the introduction of organic herbicides, cultural control practices were most widely utilized for quackgrass management. These practices did not provide acceptable control and generally interfered with the desired cropping practices. Herbicide use for quackgrass management began in the late 1950's with the introduction of simazine and atrazine. These herbicides were widely researched and used throughout the 1960's and 1970's for control of quackgrass as well as other weeds in corn. However, due to their persistence in soil, alternative herbicides were still desired. With the introduction of glyphosate in the early 1970's, many felt quackgrass as well as other problem weeds might become a thing of the past. However, these beliefs proved false and the weeds continued to flourish. With the introduction of the postemergence graminicides for soybeans in the early 1980's, corn-soybean producers had another tool for quackgrass management. However, the corn-livestock producers that could not rotate, were still left with using high rates of triazine herbicides or distraught over glyphosate cost or timing problems.

With the introduction of nicosulfuron and primisulfuron in 1990, producers have one more option for controlling quackgrass in corn. Nicosulfuron and primisulfuron have been evaluated for quackgrass control at Penn State University since 1988. The previous research at Penn State examined preplant treatments of nicosulfuron and primisulfuron in no-till corn. Preplant applications provided good quackgrass control, but corn injury proved to be a concern.

In 1991, quackgrass control research at Penn State focused on single and split postemergence applications of nicosulfuron and primisulfuron in no-till and reduced tillage corn. These treatments were compared to preplant glyphosate applications with or without tillage. In addition, a preplant application of glyphosate followed by postemergence nicosulfuron plus 2,4-D, and an early preplant application of atrazine followed by a preemergence application of simazine were included with the tillage treatments for comparison. The tillage treatments were performed with a tandem disk followed by a finishing disk ten days after glyphosate application. Alachlor and cyanazine were broadcast preemergence at 2 lb/A each over the entire study.

Preplant tillage in the absence of a quackgrass herbicide greatly reduced quackgrass competition compared to the no-till check treatment. Early season evaluations indicated that glyphosate and split atrazine/simazine treatments were superior to nicosulfuron and primisulfuron treatments, especially in the no-till plots. By two weeks after the last postemergence application (6/26), the quackgrass control was similar in all the herbicide treatments regardless of tillage (Table 1.). However, quackgrass biomass remained significantly higher and appeared to affect corn growth in the nicosulfuron and primisulfuron treated no-till plots, compared to the glyphosate and split triazine treatments. In general, quackgrass biomass was higher in the no-till plots compared to the tilled treatments. By late summer (8/21), quackgrass control levels were similar in all treatments, but biomass still remained higher in some of the sulfonylurea no-till treatments (Table 2.). Nicosulfuron appeared slightly better than primisulfuron on controlling quackgrass and little difference was observed in single versus split applications of the two herbicides. Herbicide treatments did not significantly influence corn yield, but grain yield was lower in the no-till compared to the tilled plots.

Nicosulfuron and primisulfuron performed best in a preplant tillage program. Their use in no-till appears linked to a fall or preplant glyphosate application or possibly in conjunction with a triazine herbicide program.