Suppression of Field Paspalum in Kentucky Bluegrass with Mesotrione

Abstract

Field paspalum (Paspalum laeve Michx.) is a problematic, perennial weed in lawns, athletic turf, and golf courses from Texas to New Jersey with similar biology to dallisgrass (Paspalum dilatatum Poir.). The loss of monosodium methanearsonate (MSMA) from the market requires an alternative for field paspalum control in cool-season turf. We evaluated various spring application timings, frequencies, and rates of MSMA or mesotrione applied at two-week intervals in south central Indiana over three years. MSMA applied twice at 2.0 + 2.0 lb/acre (2.25 + 2.25 kg/ha) consistently provided the lowest cover of field paspalum, whereas MSMA applied once at 2.0 lb/acre, mesotrione applied twice at 0.25 + 25 lb/acre (0.28 + 0.28 kg/ha), or mesotrione applied three times at 0.167 + 0.167 + 0.167 lb/acre (0.187 + 0.187 + 0.187 kg/ha) provided equivalent and slightly higher coverage of field paspalum than MSMA applied twice at 2.0 + 2.0 lb/acre. Applications initiated in mid to late May reduced field paspalum coverage more than earlier applications. Though mesotrione only partially reduced coverage of field paspalum with the rates and timings in our study, it has excellent turf safety on cool-season grasses and may be a suitable replacement for MSMA. However, increased efficacy is needed before mesotrione becomes commercially viable for field paspalum control.