Interference and control of large crabgrass (Digitaria sanguinalis) and southern sandbur (Cenchrus echinatus) in forage bermudagrass (Cynodon dactylon)

Field experiments were conducted at two locations in central Alabama to evaluate competitiveness of large crabgrass and southern sandbur with 'Tifton 78' hybrid bermudagrass as influenced by diuron application and sprigging rate. Large crabgrass was the more competitive species. In late season, bermudagrass ground cover with no weed competition was 96% compared with 72 and 81% where large crabgrass and southern sandbur, respectively, were present. Similarly, large crabgrass and southern sandbur reduced the proportion of bermudagrass in the cumulative harvested forage by at least 59 and 38%, respectively. Application of diuron preemergence (PRE) at 1.1 kg ai/ha was more effective than postemergence (POST) application, both in terms of weed control and bermudagrass safety. With diuron applied PRE, large crabgrass and southern sandbur reduced the proportion of bermudagrass in the harvested forage only 32 and 25%, respectively. Increasing bermudagrass sprigging rate was beneficial for weed control but of relatively minor importance compared with diuron PRE.