Annual Bluegrass Control In Bermudagrass Overseeded with Glyphosate Tolerant Perennial Ryegrass.

Annual bluegrass (Poa annua L.) is a problematic weed in perennial ryegrass (Lolium perenne L.) turf due to its lighter green color, prolific seedhead production, and infestation in golf courses, athletic fields, and home lawns. This study evaluated annual bluegrass control and the response of ‘Replay’, a glyphosate tolerant variety of perennial ryegrass, to glyphosate applications in a bermudagrass (Cynodon dactylon L.) stand overseeded with perennial ryegrass. Research was conducted at Auburn University Turfgrass Research Unit from December 2010 to April of 2011. Glyphosate was applied at 0.14, 0.28, 0.56 and 1.12 kg ae ha^-1 both singly and sequentially with a 3-weeks interval in different application times (December, January and February). Ethofumesate (Prograss^®) was applied at 1.13 kg ai ha^-1 for comparison purposes at each application time. The results indicate that glyphosate should not be applied until 8 weeks after perennial ryegrass seeding. December applications did not control annual bluegrass adequately later in the season (March and April). January applications controlled annual bluegrass best, with the January sequential application at 0.14 kg ha ^-1 controlling annual bluegrass with lower perennial ryegrass injury. February glyphosate applications were not as effective for annual bluegrass control potentially due to larger plant size at this application, but resulted in the least perennial ryegrass injury of the application timings.