Controlling Kentucky Bluegrass with Herbicide and Burning Is Influenced by Invasion Level

Abstract

Kentucky bluegrass (Poa pratensis L.) invades northern Great Plains rangelands. On the Sheyenne National Grassland in southeastern North Dakota, three research sites, each with a different level of Kentucky bluegrass invasion, were chosen to evaluate effectiveness of burning and burning–herbicide combinations to control Kentucky bluegrass. Initial Kentucky bluegrass invasion levels were 37%, 77%, and 91% for LOW, MODERATE, and HIGH invaded sites, respectively. Within each invaded site, four replicated strips (20 by 60 m) were established, with half of each strip burned in late October 2005 and the other half burned in early May 2006. Herbicide treatments of (1) no herbicide, (2) 2.24 kg ha−1 of glyphosate, and (3) 0.43 kg ha−1 of imazapic were randomly assigned to 10 by 20 m subplots within each burn. Control plots were established at the same time. Relative basal cover of native grass, native forb, and Kentucky bluegrass was estimated annually using 50 10-point frames within each subplot. On the HIGH site in 2006, fall-burned plots with a spring glyphosate application had three times the native grass cover and only one fourth of the Kentucky bluegrass cover compared with controls. Similar results with the same treatment occurred at the MODERATE site. Native grasses became the most abundant plant community on these plots in the MODERATE and HIGH sites within 1 yr. Treatment differences were transitory, and the LOW site differed from the MODERATE and HIGH sites. In 2007, on fall-burned plots with spring glyphosate application, the amount of Kentucky bluegrass was 14% and 30%, and native grass species were 52% and 42% on the MODERATE and HIGH sites, respectively, which was similar to the initial values on the LOW site. These data emphasize the importance of initial invasion level in developing restoration strategies and provide evidence burning and herbicide combinations can be valuable management tools even on heavily invaded grasslands.

Improving Ecological Restoration to Curb Biotic Invasion—A Practical Guide

“…Based on available evidence, it is reasonable to argue that the effectiveness of such control methods or treatments would depend on the degree of invasion. For example, Ereth et al (2017) recently reported that both herbicide and burning can help in controlling Kentucky bluegrass ( Poa pratensis L.) invasion, but the outcome depends on its level of invasion. Poa pratensis and smooth bromegrass ( Bromus inermis Leyss.…”

Kentucky Bluegrass Invasion in the Northern Great Plains and Prospective Management Approaches to Mitigate Its Spread

“…Additionally, native species cover was also significantly greater under alternative grazing treatments. Application of herbicide, such as glyphosate, is a popular rangeland management practice [ 31 , 32 ]. In the NGP, the combination of burning and glyphosate application during early spring and late fall when the warm season grasses were dormant showed promising results in combating Kentucky bluegrass while increasing the native grasses [ 32 ].…”

“…Application of herbicide, such as glyphosate, is a popular rangeland management practice [ 31 , 32 ]. In the NGP, the combination of burning and glyphosate application during early spring and late fall when the warm season grasses were dormant showed promising results in combating Kentucky bluegrass while increasing the native grasses [ 32 ]. Thus, alteration in traditional practices could be a potential strategy to control the Kentucky bluegrass invasion while improving the overall native species cover.…”

“…Dislocation and replacement of native species by specific invasive species often transform a highly diverse ecosystem into a homogenized emerging or novel ecosystem [ 28 , 29 ]. Traditional management practices that are used to control Kentucky bluegrass include prescribed fire, grazing, application of herbicides, and a combination of these tactics [ 19 , 29 , 30 , 31 , 32 ]. As Kentucky bluegrass morphological and physiological traits resemble those of many surrounding native cool-season grasses, controlling this species with traditional management practices also can impair the growth and spread of those native species [ 6 , 30 ].…”

Kentucky bluegrass invaded rangeland: Ecosystem implications and adaptive management approaches

“…8,23 Even so, past studies in the northern Great Plains have found prescribed fire can reduce the cover of Kentucky bluegrass. [24][25][26] For example, Kral et al 26 found that burning in May, September, or November resulted in reduced Kentucky bluegrass cover and increased plant species diversity. After September prescribed fires, reduced Kentucky bluegrass cover persisted for at least 3 years, while cover increased to pre-fire levels after 1 year following May burning.…”