Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass (Digitaria species) Control in Turfgrass.

Seven field trials were conducted in Connecticut, Indiana, Michigan, New Jersey, North Carolina, and Pennsylvania (2) in 2008 to evaluate postemergent application of liquid dithiopyr and fenoxaprop for control of crabgrass (Digitaria species) in turfgrass.  For each trial, five foot by five foot plots were replicated three times for each individual treatment.  CO2 backpack sprayers were used to apply all treatments at the one to three or three to five tiller stage of crabgrass development.  The turf plots were maintained with regular mowing and watering and received no fertilization.  Percent crabgrass control evaluations were made in August.

When applied at the one to three tiller stage of crabgrass development, reduced rates of dithiopyr at 140 g ai/Ha + fenoxaprop at 70 g ai/Ha (68% control) and dithiopyr at 140 g ai/Ha + fenoxaprop at 100 g ai/Ha (71% control) provided comparable crabgrass control to the X rate of fenoxaprop at 140 g ai/Ha (67% control).  When applied at the three to five tiller stage of crabgrass development, reduced rates of dithiopyr at 140 g ai/Ha + fenoxaprop at 70 g ai/Ha (95% control) and dithiopyr at 67 g ai/Ha + fenoxaprop at 100 g ai/Ha (97% control) provided comparable crabgrass control to the X rate of fenoxaprop at 140 g ai/Ha (93% control).