Mesotrione for Annual Weed Control in Established and Newly Seeded Turf.

Three studies were conducted at Iowa State University to evaluate mesotrione as a pre- and postemergence control of annual grassy weeds in Kentucky bluegrass (Poa pratensis L).  An additional study evaluated mesotrione for the spring establishment of Kentucky bluegrass and perennial ryegrass (Lolium perenne L).  Granular mesotrione applied as a preemergence at 0.28 kg a.i ha^-1 provided 8% control of crabgrass (Digitaria spp.) at the end of season, whereas 0.28 kg a.i ha^-1 mesotrione combined with 0.56 kg a.i. ha^-1 prodiamine resulted in 92% control of crabgrass during the same rating period.   Studies evaluating preemergence liquid formulations concluded that 0.28 kg a.i ha^-1 mesotrione reduced crabgrass by 35%, whereas a combination of 0.28 kg a.i ha^-1 mesotrione and 0.84 kg a.i. ha^-1 prodiamine resulted in 99% control.   Early postemergence applications of liquid mesotrione alone at 0.28 kg a.i ha^-1 provided 94% control of crabgrass. The spring seeding study compared mesotrione to siduron.  Neither mesotrione nor siduron had any detrimental effects on the germination and growth of Kentucky bluegrass and perennial ryegrass seed.  At the end of the season, plots treated with 0.21 kg a.i ha^-1 mesotrione at seeding and 7 weeks following seeding resulted in 25% more cover of Kentucky bluegrass and 16% more cover of perennial ryegrass than the control.  Siduron at 6.7 kg a.i ha^-1 at seeding provided 45% more cover of Kentucky bluegrass and 34% more cover of perennial ryegrass.  Siduron-treated plots provided excellent crabgrass control, but were heavily infested with carpetweed (Mollugo verticillata L) .  Mesotrione effectively controlled the carpetweed.