The Control of Various Bermudagrass Cultivars in Tall Fescue Utilizing Fenoxaprop & Fluazifop

Bermudagrass (Cynodon dactylon (L). Pers.) is considered to be one of the most difficult to control grass weeds in turf throughout the U.S. Recent breeding efforts have produced much more desirable bermudagrass cultivars, and therefore its use has increased. Ironically, as bermudagrass use becomes more popular it poses even greater difficulties to the turf manager. The need to control these warm season turfgrass species, without causing injury to other desirable turfgrass species, is one of the most intractable problems a turf specialist encounters. Herbicides previously used to selectively control bermudagrass such as siduron and oxadiazon have proven to be of only minimal efficacy or to induce significant injury to other desirable turfgrasses. Tests conducted in 1993, 1994 and 1995 have indicated that fenoxaprop plus fluazifop (Horizon 2000R) controlled bermudagrass effectively. Six bermudagrass (Cynodon dactylon) cultivars and tall fescue (Festuca arundinacea) were used in the susceptibility studies. Visual control and cover ratings were taken at two-week intervals until ten weeks after the final treatment. Sequential applications of labeled rates of fenoxaprop or fluazifop alone only temporarily controlled bermudagrass shoots. Horizon 2000 applied at 0.40 kg ai/ha in three sequential applications proved effective in controlling bermudagrass rhizomes and stolons. From results of previous studies and research conducted here it has been hypothesized that synergistic effects of fenoxaprop on fluazifop allow both differential control of various bermudagrass cultivars and increased tall fescue tolerance to these herbicides.