Effect of Reduced Dithiopyr and Prodiamine Rates on Large Crabgrass (Digitaria sanguinalis) Control in Common Bermudagrass (Cynodon dactylon) and Tall Fescue (Festuca arundinacea) Turf

Abstract

Dithiopyr and prodiamine are new preemergence herbicides for crabgrass control in tall fescue and bermudagrass turf. A field experiment was conducted over a 2-yr period to determine the lowest rates of dithiopyr and prodiamine needed to control large crabgrass effectively in tall fescue and common bermudagrass. Prodiamine applied at 0.17 kg ai/ha in each of two applications controlled 92 to 93% of large crabgrass by late August in common bermudagrass and 78 to 85% in tall fescue. Dithiopyr applied at 0.11 kg ai/ha in each of two applications controlled 85 to 89% of large crabgrass in common bermudagrass, but the control was not consistent across years at any rate in tall fescue. Dithiopyr applied at 0.56 kg/ha on tall fescue controlled 91% of large crabgrass in 1993, but only 38% in 1994. The higher control with dithiopyr in common bermudagrass was due to greater competition with germinating large crabgrass seeds and emerging seedlings during the summer, compared with little or no competition from tall fescue. The quality of tall fescue and common bermudagrass treated with dithiopyr and prodiamine was generally higher in plots where large crabgrass was effectively controlled than in plots with poor control. In general, dithiopyr did not control large crabgrass as effectively in tall fescue as in common bermudagrass, while the control with prodiamine was similar for the two turfgrass species.