Paragrass is a nonnative category I invasive species in central and south Florida. This perennial grass species outcompetes native vegetation and is capable of rapid spread by vegetative reproduction. Although glyphosate and imazapyr are effective herbicides for paragrass control, the use of herbicides in certain areas may be restricted because of application timing or environmental concerns. Therefore, our objectives were to examine the effect of water depth (saturated vs. flooded) after burning or cutting, and the effect of water depth and duration after simulated roller-chopping, on paragrass regrowth under controlled conditions. In the first study, paragrass plants were cut or burned with a propane burner to 1 cm (0.39 in) above the soil surface. Plants were either watered daily (control), or were subjected to one of two water treatments: water level at the soil surface (saturated) or flooded to a depth of 44 cm. Burned-saturated or burned-flooded plants had 92% less biomass 5 wk after treatment (WAT) than cut-saturated plants. Flooding resulted in plant death regardless of the plant treatment. In the second study, simulated roller-chopping was performed by cutting paragrass stolons into one-, two-, or three-node segments; planting them into flats; and subjecting them to water treatments for 3, 7, 14, 28, and 42 d. Burning, cutting, and roller-chopping could be useful to control paragrass if subsequent flooding is applied. Future research should focus on evaluating the response of these control techniques in natural areas where water depth can be managed.
Nomenclature: Paragrass, Urochloa mutica (Forsk.) T. Q. Nguyen.
Management Implications: Paragrass is a highly invasive perennial grass species that invades wetland ecosystems of central and south Florida as well as other tropical areas of the world. Invasion of paragrass into such ecosystems typically reduces native species diversity and abundance, and ultimately results in monotypic swards, an unsuitable wildlife habitat. The effect of water depth (saturated vs. flooded) after burning or cutting, and the effect of water depth and duration after simulated roller-chopping on paragrass regrowth were examined under controlled conditions. Burning, cutting, and simulated roller-chopping did not reduce paragrass regrowth without either soil saturation or inundation. In saturated conditions, burning significantly reduced all variables of plant growth compared to cutting. However, both burning and cutting killed paragrass equally when flooded for a period of 5 wk. At least 17 d of flooding or 29 d of saturated conditions were required to reduce paragrass biomass by 90% under our conditions. These results suggest that soil saturation or flooding is required after cultural techniques have been employed. Cutting or burning of paragrass followed by flooding may be an option for natural area managers in areas where herbicides may not be applied due to timing or environmental reasons. Roller-chopping followed by flooding could be an effective option to paragrass control where burning would not possible because of location and timing.
