Dallisgrass (Paspalum dilatatum) control with foramsulfuron in bermudagrass turf.
Dallisgrass (P. dilatatum) response to various MSMA and foramsulfuron combinations was evaluated in hybrid bermudagrass (Cynodon transvaalensis × C. dactylon) from 2004 through 2006 in North Carolina, USA. Dallisgrass control declined with the herbicide rates; therefore, only the highest rates (foramsulfuron, 0.15 kg a.i./ha, and MSMA, 2.5 kg a.i./ha) were considered. Foramsulfuron followed by (fb) foramsulfuron at one week after the initial treatment (WAIT) provided 60% control of dallisgrass at one month after the initial treatment (MAIT), but control declined to 40% at 3 MAIT. MSMA (2.5 kg a.i./ha) applied 3 times provided 89% dallisgrass control at one MAIT, but the control declined to 71% at 3 MAIT. Among the 22 MSMA and foramsulfuron sequential application programmes, MSMA fb foramsulfuron at 2 WAIT fb MSMA at 3 WAIT provided the highest control (94%) of dallisgrass at one MAIT, and the control levels remained high (93%) at 3 MAIT. This herbicide programme provided 85% control at one year after the initial treatment (YAIT), whereas no other treatment provided greater than 37% control at one YAIT. The timing of foramsulfuron application following initial MSMA application affected the control of dallisgrass. Delaying the application of foramsulfuron until 2 WAIT rather than one WAIT increased the control of dallisgrass by 20% at one MAIT and 19% at 3 MAIT. However, the increase in the control at one YAIT was only 5% regardless of the herbicide rate. The addition of a second application of MSMA following the application of foramsulfuron at 2 WAIT of MSMA further increased control by 10% at one MAIT, 37% at 3 MAIT, and 48% at one YAIT. The results suggested dallisgrass may be controlled with the application of MSMA fb foramsulfuron at 2 WAIT fb MSMA at 3 WAIT applied during early to mid-summer. The use of MSMA was required to achieve dallisgrass control; however, the relatively high level of control achieved at one YAIT with a programme including sequential applications of MSMA and foramsulfuron may help reduce the total amount of arsenical herbicides used to control dallisgrass infestations over time.