Selective Control of Common Bermudagrass in St. Augustinegrass

Common bermudagrass [ Cynodon dactylon (L.) Pens.] is the most troublesome weed in commercially produced St. Augustinegrass ( Stenotaphrum secundatum (Walter) Kuntze] sod due to inadequate selective control methods. Currently available herbicides are nonselective and require multiple applications, which delays replanting, and cause significant St. Augustinegrass injury. Research was conducted to evaluate several herbicides for selective control of common bermudagrass in ‘Floratam’ St. Augustinegrass. Herbicides included ethofumesate [(±)2‐ethoxy‐2,3‐dinydro‐3,3‐diinethyl‐5‐benzofuranyl methanesulfonate] and ethofumesate plus either flurprimidol [αa‐(1‐methylethyl)‐α‐[4‐trifluourmethoxyy)phenyl]‐5‐pyrimidinemethanol], atrazine [6‐chloro‐ N ‐ethyl‐ N ′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], or siduron [ N ‐(2‐methylcyclohexyl)‐ N ‐phenylurea]. Excellent (>95%) common bermudagrass control followed sequential applications of ethofumesate plus atrazine applied in March, April, and May. Good control (80–89%) was observed with ethofumesate alone applied the same months. Inconsistent and/or poor control (<70%) of common bermudagrass was obtained with ethofumesate plus either flurprimidol or siduron. Additional treatments made in February and/or in November of the previous year did not increase control. St. Augustinegrass turf quality was unaffected by ethofumesate plus atrazine. Turf quality was reduced 4 to 8 wk after repeat applications of ethofumesate plus siduron. Ethofumesate plus flurprimidol combinations reduced turf quality for 8 to 12 wk. Properly timed ethofumesate plus atrazine applications is the first reported means of selectively controlling common bermudagrass in St. Augustinegrass turf.