Rehabilitation of native prairie remnants invaded by smooth brome and Kentucky bluegrass in the northern Great Plains

Smooth brome (Bromus inermis) and Kentucky bluegrass (Poa pratensis) are introduced cool-season perennial grasses known to invade grasslands throughout North America. During the fall of 2005 and spring of 2006, we implemented a removal study at 6 native prairie sites in eastern South Dakota invaded by smooth brome and Kentucky bluegrass. Treatments included five herbicide combinations and a fall burn to determine the potential of each for renovation of invaded native grasslands. The herbicide combinations were applied in the fall and spring to determine optimum timing for control. Across sites, control plots averaged 28% and 33% cover by smooth brome and Kentucky bluegrass, respectively. Smooth brome cover on herbicide treated plots ranged from 1 to 14% and Kentucky bluegrass cover ranged from 2 to 24%. Smooth brome cover was similar between fall burned and control plots (21% to 28%), but Kentucky bluegrass cover was significantly lower (12% to 33%). Native plants showed a similar increase across fall (burn and herbicide) treatments, but spring treatments had a detrimental effect on both native grasses and forbs. Several herbicide combinations show potential for removal of smooth brome, while causing minimal harm to native species.