Annual bluegrass populations on Kentucky bluegrass used for lawns, sports fields, golf course roughs and fairways often contain high percentages of annual or intermediate types that are more susceptible to post-emergence control programs. There is a body of research on the three products that are available for use at this time. Prograss (ethofumesate), Velocity (Bispyrac-sodium) and Tenacity (mesotrione). Velocity is not recommended on KBG due to the potential turf injury known to occur on certain Midnight type and aggressive compact types. The best Prograss programs on Kentucky bluegrass are 2 qts./A of the EC formulation applied in November, December and March. Now this will require some modification if you go north of the Thruway based on air temp. Tenacity has been more heavily researched the last few years and significant refinements to annual bluegrass control programs have been made. First, studies show consistently that applications in conjunction with soluble N fertilizer that stimulates annual bluegrass growth will significantly increase efficacy. As little as one half pound of N per 1000 improves control 40%. Overseeding also enhances annual bluegrass control with perennial ryegrass or Kentucky bluegrass. Again overseeding increases control 30%. Finally there are at least two application required at the 5 to 8 oz per acre rate at two week intervals. Some studies have investigated 5-10 applications, and while they work well and often do not increase injury, they exceed the labelled rate allowance for a season.