EVALUATION OF AMINOCYCLOPYRACHLOR FOR SELECTIVE WEED CONTROL IN TURF. J.M. Johnson*, K. Lloyd, and J. Sellmer, Penn State, University Park, PA (49)


   Broadleaf weed control improves aesthetics, enhances turf integrity, and assures roadside safety. Effective management programs utilize herbicide rotations and integrate novel chemistries in order to prevent herbicide resistance. A new synthetic auxin, aminocyclopyrachlor, was evaluated in combination with other active ingredients for dicot weed control and safety to turf. 
   Spring and late summer trials were established at two trial sites in Blair county, PA using several tank mix combinations of: aminocyclopyrachlor mixed with chlorsulfuron, metsulfuron, or rimsulfuron; aminopyralid alone or combined with imazapic or metsulfuron; and untreated checks. All herbicide treatments included a nonionic surfactant at 0.5 percent v/v. Studies were arranged in a randomized complete block design with three replications. Treatments were applied at a rate of 374 L/ha, using a CO2-powered sprayer. At trial site 1, treatments were applied to 7 by 9 m plots on September 24, 2009 and May 6, 2010. At trial site 2, treatments were applied to 2 by 8 m plots on May 28 and August 25, 2010. Initially, the percent total cover and cover by species was recorded. Subsequent ratings evaluated percent injury or phytotoxicity to turf and injury or control of select broadleaf species. An analysis of variance was conducted using Fisher’s Protected LSD and a significance level of 0.05.
   Control of broadleaf plantain, aster, red clover, dandelion, and wild carrot at the first site was 98 percent or greater at 224 d after treatment (DAT) and 117 DAT for the fall and spring-applied treatments, respectively, of aminocyclopyrachlor at 132 g/ha plus chlorsulfuron at 53 g/ha or metsulfuron at 21 g/ha. Injury to tall fescue was noted using metsulfuron at rates as low as 21 g/ha; however, by 117 DAT the effects were not noticeable. At site 2, chicory and goldenrod cover were completely eliminated with spring-applied treatments of aminocyclopyrachlor plus chlorsulfuron or metsulfuron with rates as low as 132 g/ha plus 26 g/ha or 66g/ha plus 11 g/ha, respectively, by 105 DAT. The higher rate of 132 g/ha aminocyclopyrachlor combined with chlorsulfuron was needed to gain full control of goldenrod. Fall-applied treatments of 132 g/ha aminocyclopyrachlor plus 53 g/ha chlorsulfuron or 21 g/ha metsulfuron resulted in 96 to 100 percent injury to chicory, 68 to 72 percent injury to goldenrod, and 43 to 60 percent injury to aster at 30 DAT. The aminocyclopyrachlor plus chlorsulfuron or metsulfuron tank mixes did not result in unacceptable injury to tall and fine fescue. In contrast, aminocyclopyrachlor plus rimsulfuron or aminopyralid plus imazapic did cause initial and unacceptable injury to tall and fine fescue or tall fescue, respectively.
   The aminocyclopyrachlor plus chlorsulfuron or metsulfuron combinations and rates evaluated in these studies provided effective control of all broadleaf species tested, except goldenrod and aster, and demonstrated equal or improved control to the other mixes tested. At higher rates aminocyclopyrachlor increased control of goldenrod.