Sequential applications of preemergence and postemergence herbicides for large crabgrass (Digitaria sanguinalis) control in tall fescue (Festuca arundinacea) turf.
Pre-emergence (pendimethalin, prodiamine, dithiopyr, oryzalin and oxadiazon) and post-emergence (MSMA and fenoxaprop) herbicides were sequentially applied to Festuca arundinacea turf during 1995-96 in Georgia, USA, to determine the lowest herbicide rates needed for acceptable control of Digitaria sanguinalis. Prodiamine (0.3 and 0.8 kg/ha) resulted in 85 and 96% weed control, respectively. Sequential applications of oxadiazon (1.1 kg/ha) in late February, followed by fenoxaprop (0.2 kg/ha) in June resulted in 85% weed control in late August. Control was similar in mid-August, when pendimethalin (1.1 kg/ha), dithiopyr (0.2 kg/ha) or oryzalin (0.8) was followed by fenoxaprop (0.2 kg/ha), but control was ≤74% by late August. Better weed control was found in combinations with fenoxaprop than in combinations with MSMA (2.2 kg/ha). The turf quality was not affected by prodiamine, dithiopyr and oxadiazon. In 1996, pendimethalin (3.3 kg/ha) and oryzalin (2.2 kg/ha) reduced turf quality by 16 and 46%, respectively. In 1995, MSMA reduced crop quality by ≤21% as compared to fenoxaprop (≤10%). Sequential herbicide programmes did not affect turfgrass quality as compared to single treatments.