Fall and/or Spring Applications of Granular Dithiopyr and Prodiamine for Crabgrass (Digitaria species) Control in Turfgrass.

Three field trials were conducted in Indiana (2006-2007 and 2007-2008) and Pennsylvania (2007-2008) to evaluate fall and/or spring applications of granular dithiopyr and granular prodiamine 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.  Shaker bottles or shaker tables were used to uniformly spread the granular treatments over the treated plots.  Treatments were applied to individual plots in October, November, November followed by May, March, April, May, or June.  The turf plots were maintained with regular mowing and watering and received no fertilization.  Percent crabgrass control evaluations were made in July (Indiana 2007) and August (Indiana 2008 and Pennsylvania 2008).

Fall applications (October and November) of dithiopyr at 560 g ai/Ha and fall application followed by (fb) spring application (November-May) of dithiopyr at 560 fb 280 g ai/Ha provided acceptable crabgrass control.  Fall applications (October and November) of prodiamine at 730 g ai/Ha did not provide acceptable crabgrass control.  Fall application followed by spring application (November-May) of prodiamine at 730 fb 280 g ai/Ha provided acceptable crabgrass control.  March, April, and May applications of dithiopyr at 430 or 560 g ai/Ha provided acceptable crabgrass control while June application did not.  March and April applications of prodiamine at 730 g ai/Ha provided acceptable crabgrass control while May and June applications did not.  March, April, May, and June applications of dithiopyr at 430 g ai/Ha and prodiamine at 730 g ai/Ha were not significantly different in crabgrass control.