Annual Bluegrass Control in Overseeded Fairway Turf after Applications of Five PGR Products, with or without Previous Applications of Ethofumosate Herbicide.

Early post emergence control of annual bluegrass from two late fall applications of ethofumosate (Prograss) herbicide is a typical standard practice for post overseed control of annual bluegrass, but often some plants either survive or germinate in the spring, requiring further weed control.  Five PGR products were applied to fairway infested turf which did or did not receive previous applications of ethofumosate on 20 Jan and 2 Feb.  PGR products were applied on five dates (on 17 Feb, 10 Mar, 29 Mar, 10 April, and 5 May 2016) to 1.5 X 1.8 meter plots replicated 4 times. PGR products and formulated product application rates included  Cutless (flurprimidol 2.8 kg/ha); Musketeer (flurprimidol, paclobutrazole and trinexapac-ethyl 2.52 kg/ha); Legacy (flurprimidol, trinexapac ethyl 1.75 kg/ha); Trimmit (paclobutrazole 0.63 kg/ha) and Anuew (prohexadione sodium) (0.56 kg/ha). Turfs were rated throughout the spring  for percent plot Poa annua cover, which was used to calculate percent weed control as 1-(treated/control) x 100.  Percent weed control was 98% in March for Prograss alone treated turf, which decreased to 80% from mid-April to mid-May.  When applied alone, PGR products peaked in April and May with 60%-99%  weed control, as Musketeer had 97-99% weed control in mid-April and May, respectively. Anuew provided 78% and 50% control for the same periods, respectively. When applied alone (not on Prograss treated turf), Musketeer, Legacy and Trimmitt had the greatest overall weed control. When PGR products were applied over Prograss treated turfs, annual bluegrass weed control was maintained at 97-100% in March, and 96-98% during the first week of May. When applied over turf previously treated with Prograss, the PGR products added about 20% weed control in April, 15% in May and 10 % by mid-May. When applied over ethofumosate treated turf, Musketeer, Legacy and Trimmit, maintained weed control levels of 95% or greater in March and April. This data demonstrates that the same PGR products which had the greatest effect on Poa annua when applied alone, also enhanced the long term weed control of oveseeded turfs which previously received two applications of ethofumosate.