Effects of a New Herbicide (Aminocyclopyrachlor) on Buffalograss and Forbs in Shortgrass Prairie

Abstract

Herbicides used to control many forb species in pastures may injure desirable native grass species. Buffalograss, a major component of shortgrass rangeland, often is injured by some growth regulator herbicides, such as 2,4-D and dicamba. Aminocyclopyrachlor (formerly known as DPX-MAT28 and herein termed ACPCR), a new synthetic auxin herbicide chemistry for control of broadleaf weeds, was investigated for injury to buffalograss and control of forbs in shortgrass prairie at varying rates of application. In the season of application, ACPCR at rates of 140 g ai ha−1or less caused buffalograss injury that was either negligible or short-lived, and visual estimates of grass injury were 8% or less at the end of the growing season. At ACPCR rates of 280 g ha−1, more injury was evident at 3 wk after treatment (WAT) than at the end of the season if adequate precipitation was available for new leaf growth. When precipitation was lacking, evidence of injury persisted through to the end of the season when treated at the greatest rate of ACPCR. Buffalograss injury was mainly in the form of browned leaf tips, but total buffalograss dry matter yield was not different between any treatments in either year. The year after treatment, no buffalograss injury was evident from any of the herbicide rates. Final forb control was 97% or greater each year for ACPCR at the 140 and 280 g ha−1rates. In this experiment, rates as low as ACPCR at 140 g ha−1provided excellent forb control and maintained buffalograss productivity.

Bahiagrass Tolerance to Aminocyclopyrachlor in Florida

“…In previous research buffalograss exhibited 28% leaf tip necrosis 3 WAT with 240 g ai ha À1 ACP (Harmoney et al, 2012). Comparatively, injury on both bahiagrass cultivars was ,20% following application of the same rate of ACP at 15, 30, and 60 DAT, and this was similar to research conducted by Durham et al (2016), where 'Pensacola' bahiagrass injury did not exceed 25% within the rate range of 49 to 132 g ai ACP ha À1 .…”

“…This could be due to the increased rainfall in 2013 and 2014 than in 2012 (data not shown) resulting in slower bahiagrass recovery. However, an inverse relationship on rainfall and ACP injury was observed with buffalograss where higher injury was observed when higher rainfall occurred (Harmoney et al 2012). In spite of initial injury on buffalograss, biomass production was not affected at the end of the growing season (13 WAT) over 2 yr (Harmoney et a Abbreviations: ACP, aminocyclopyrachlor; DAT, days after treatment.…”

“…J.T. Columbus], a shortgrass plains forage species, exhibited 28% leaf tip necrosis 3 WAT with 240 g ai ha À1 ACP (Harmoney et al 2012). However, buffalograss biomass production was not affected at the end of growing season (13 WAT; September) over 2 yr.…”

Effects of Aminocyclopyrachlor Herbicide on Downy Brome (Bromus tectorum) Seed Production under Field Conditions

“…Because aminocyclopyrachlor (Anonymous 2009, Lindenmayer et al 2011 and aminopyralid (Senseman 2007) have soil residual properties, it may be possible to use these herbicides to reduce the downy brome seed bank and facilitate the restoration of native or improved plant communities (Harmoney et al 2012). How aminocyclopyrachlor or aminopyralid treatments will affect plant community composition may be difficult to predict.…”

Tolerance of Bermudagrass and Stargrass to Aminocyclopyrachlor

“…Additionally, buffalograss [Bouteloua dactyloides (Nutt.) Columbus], a short-prairie forage species, exhibited 28% leaf tip necrosis 3 wk after treatment (WAT) with 240 g ha À1 ACP (Harmoney et al 2012). However, buffalograss biomass production was not affected at the end of the growing season (13 WAT) over 2 yr.…”