Deertongue is a perennial, warm-season grass, and is problematic in naturalized areas of golf courses due to limited control options. Research was conducted to evaluate several herbicides for deertongue control in naturalized areas consisting primarily of fine fescue. Greenhouse studies assessed 24 herbicide admixtures and indicated that fluazifop, glyphosate, imazapic, and thiencarbazone + iodosulfuron + dicamba (TID) reduced deertongue biomass by >80% at 10 wk after initial treatment (WAIT). Subsequent field trials were conducted on golf course naturalized areas. The first site was on a woodland edge and was partially shaded for 6 h each day, and the second trial site was 50 m away from the woodland edge and not subjected to more than 1 h of daily shade. At 9 WAIT, fluazifop at 420 g ai ha^-1 applied once or three times at 3-wk intervals and topramezone at 37 g ai ha^-1 applied thrice at 3-wk intervals injured fine fescue by ≤10% at both sites. Glyphosate applied at 1,120 g ae ha^-1, imazapic at 105 g ai ha^-1, and imazapic at 53 g ai ha^-1 tank-mixed with glyphosate at 560 g ae ha^-1 injured fine fescue by ≥50% under shaded conditions, whereas glyphosate alone did not injure fine fescue under sunny conditions. Fine fescue was completely recovered by 52 WAIT from injury following herbicide treatments, except for glyphosate-containing treatments at the shaded site and glyphosate + imazapic at both sites. At 52 WAIT, glyphosate-containing treatments and sequential applications of fluazifop controlled deertongue by ≥93% and reduced shoot density to ≤5 shoots m^–2 averaged over both sites. Fluazifop at 420 g ha^-1 applied thrice at 3-wk intervals selectively controls deertongue with excellent safety to fine fescue. Glyphosate also controls deertongue, but unacceptably injures fine fescue when managed under shaded conditions. Future research will assess how different light intensities influence fine fescue epicuticular wax deposits and associated response to glyphosate.

Nomenclature: Dicamba; fluazifop; glyphosate; iodosulfuron; imazapic; thiencarbazone; topramezone; deer tongue, Dichanthelium clandestinum L. (Gould); fine fescue, Festuca spp.