Management Information on Panicum repens

In a study performed by Hanlon and Langeland (2000) on the effects of certain herbicides on P. repens , they concluded that, "Although P. repens was controlled in some areas, little or no long-term control was observed at 16 of the 26 treatment locations. To reduce the uncertainty associated with predicting long-term treatment affects, additional studies are needed to determine whether environmental factors such as periphyton mats, plant thatch, hydroperiod and water depth affect treatment efficacy." The results of Hanlon and Langeland's (2000) study can be viewed in this management information under Chemical and Fire control. David (1999) states that in his study, "One of the plans primary objectives was to restore native wetland plant communities and control P. repens . A monitoring program was initiated in 1988 to assess the first phase of restoration which involved plugging drainage ditches at strategic locations to increase hydroperiod (i.e., depth and duration of flooding)." Brecke et al. (2001) state that, "Poor sanitation practices associated with tillage operations in turfgrass, such as core aerification, can lead to the spread of this perennial weed."

Physical : Hanlon and Langeland (2000) state that, "In areas where plant biomass was reduced by fire prior to being treated with 0.84 or 1.12 kg ae imazapyr/ha, P. repens was controlled for more than two years and native plant species, including duck potato ( Sagittaria lancifolia L.) and pickerelweed ( Pontederia cordata L.) became the dominant vegetation in less than one year."

Refering to mechanical control, PIER (1999) states that, "Physical control of P. repens is difficult because of extensive rhizomes beneath soil surface. Tillage only encourages its growth."

Chemical : Williams et al. (2003) state that, "For any herbicide to be effective in controlling P. repens , a sufficient dose must be absorbed by or be translocated into the rhizomes." Data from a study conducted by Sutton (1996) states that, "Herbicide treatments for control of P. repens problems must kill all the rhizomes since a few nodes have the potential to produce a large amount of plant material in a short period of time."

McCarty et al. (1993) state that, " P. repens has invaded fine turfgrasses in the Southern U.S. due to its tolerance to most commonly used turfgrass herbicides. Research was conducted to determine P. repens tolerance to quinclorac and tank-mix combinations with other turf herbicides. Quinclorac rates in excess of 2.2 kg ai/ha were required for control (greater than or equal to 80%) of P. repens . Sequential applications were more effective than single applications. Generally, sequential applications made 3 wk after the initial were more effective than delaying sequential applications until 4 wk after the initial application. Sequential applications of quinclorac plus imazaquin (1.1 + 0.6 kg/ha) increased P. repens control (approximate 35%) as compared to quinclorac plus MSMA (1.1 + 1.1 kg/ha) but also decreased turf quality versus quinclorac applied alone or in combination with MSMA. Quinclorac applied at 2.2 kg/ha followed by 1.1 kg/ha applied 3 or 6 wk after the initial controlled P. repens best with least reduction in bermudagrass quality. Quinclorac is the first herbicide reported to selectively control P. repens in bermudagrass turf." Busey (2003) reports that, "Removal of P. repens using quinclorac would require at least several years of split-application treatments, based on the 80% reduction of total dry weight observed after 2 yr of the 0.42 kg/ha four-way split application. The benefit from multiple split applications is probably due to starving the underground storage of new photosynthate; thus the greater the number of weeks that canopy is suppressed, the less new underground storage occurs."

Jenkins et al. (2004) report that, "the herbicide imazapyr primarily controlled non-native or other native species with the exception of the non-native P. repens (torpedo grass), which was not adversely affected." Hanlon and Langeland (2000) conducted a study evaluating imazapyr's or a combination of imazapyr and fluridone as control agents of P. repens . The authors state that, " P. repens was controlled for more than one year in some areas following a single aerial treatment using 0.56, 0.84, or 1.12 kg acid equivalents (ae) imazapyr/ha. Combining imazapyr and fluridone did not increase the level of P. repens control. "

In a study conducted by Hossain et al. in 1997 concludes that, Asulam was found to be the most effective herbicide for controlling this weed in sugarcane. Asulam is used to control Sorghum halepense in sugarcane in the USA (Millhollon 1976; Richard & Griffin 1993, in Hossain et al. 2001)." The authors conclude from their study that, "From the results of this study, it was suggested that Asulam can be used for P. repens control in sugarcane in both the spring and summer seasons, even though the trials were not repeated in the same season (Hossain et al. 2001b)."

Biological : In the study performed by David (1999) the author states that, "Ditch plugs proved an effective method for restoring over drained small wetlands. The presence of native wetland plants, especially P. hemitomon , may be critical in helping control the exotic P. repens , a plant species that can spread aggressively in a short time period ( Sutton 1996). Dense stands of P. hemitomon appeared to impede the spread of P. repens , suggesting some direct competition occurred between these species. Wetland management that favors P. hemitomon should be encouraged P. repens grass control is desirable."