Simulated controlled-release mesotrione for turfgrass tolerance and weed control

Mesotrione typically requires multiple applications to control emerged weeds in turfgrass. As it is absorbed by both foliage and roots, a controlled-release (CR) formulation could eliminate the need for multiple applications. Research was conducted to evaluate simulated-release scenarios that mimic a potential CR mesotrione formulation. A soluble-concentrate formulation of mesotrione was titrated to produce a stepwise change in mesotrione rates, which were applied daily to mimic predetermined release scenarios over a 3-wk period. CR scenarios were compared to a broadcast treatment of mesotrione at 280 g ai ha(-1) applied twice at 3-wk intervals, and a nontreated. Mesotrione applied in three temporal-release scenarios controlled creeping bentgrass, goosegrass, nimblewill, smooth crabgrass, and white clover equivalent to the standard sprayed mesotrione treatment in every comparison. However, each CR scenario injured tall fescue two to seven times more than the standard treatment. Soil- and foliar-initiated repeat treatments were equivalent in most comparisons. Our data indicate that mesotrione applied in a temporal range to simulate controlled-release scenarios can deliver desired weed control efficacy comparable to sequential broadcast applications. More research is needed to elucidate proper timings and release scenarios to minimize turfgrass injury.