Common Bermudagrass Encroachment Resistance of Three Hybrid Turf Bermudagrasses.

Utilization of improved bermudagrass (Cynodon species) varieties is often confounded due to inability to eradicate pre-existing bermudagrass from the use site. Consequently, the newly installed variety often becomes contaminated. This results in reduced visual and functional quality of the turf. Patriot (OKC 18-4), TifSport (Tift 94) and Tifway (Tifton 419) hybrid bermudagrasses (C. dactylon X C. transvaalensis) were evaluated for their ability to compete against an aggressive locally adapted turf-type common bermudagrass (C. dactylon ‘TGS U-3') under simulated golf course fairway conditions.  Newly sprigged plots of each variety were contaminated with three sprigs per plot (4 cm in length) of the contaminant TGS U-3. The experiment was conducted a total of three times and spanned the period 2005-2009 for Experiment (Exp) I and 2006-2009 for Exp II and III. Sprigging was at 21 m³ ha^-1 with the contaminant placed shortly thereafter. Management included mowing at 1.3 cm as needed, irrigation to prevent wilting and total season nitrogen input of 196 kg ha^-1 yr^-1. Colonization (percent living cover) of the plot by the designated cultivar and the contaminant was visually assessed at 0, 2, 4, 6, and 8 weeks after sprigging and thereafter once per month during the year of establishment using a 100 point grid. In 2007 plot coverage was monitored at the beginning and end of the growing season. Coverage was not measured in 2008 and final coverage was assessed once in 2009. In one Exp sprigging was conducted on 9 June 2006. Patriot provided significantly higher living cover (52, 95 and 99%) on 26 June, and on 14 and 31 Jul 2006 than did TifSport or Tifway. TifSport cover (9, 44 and 67%) did not differ from Tifway cover (9, 42 and 64%) on these same sampling dates. TGS U-3 cover on 14 Jul averaged 4, 0.2 and 5% (LSD = 1) in the TifSport, Patriot and Tifway plots while on 31 Jul 2006 it averaged 21, 0.5 and 23% (LSD=4), respectively. During the first season's research Patriot colonized ground more rapidly than either Tifway or TifSport and more effectively competed against a localized aggressive common bermudagrass than did Tifway or TifSport. Research is on-going and the findings from subsequent years will be discussed.