Fineleaf Fescue Species and Variety Tolerance to Glyphosate

Abstract

AbstractSome fineleaf fescues have demonstrated tolerance to glyphosate, and this broad-spectrum, nonselective herbicide would be a valuable tool for controlling various weeds in low-input turf areas. A study was conducted to evaluate tolerance of 56 fineleaf fescue varieties to glyphosate applied at 0.0, 0.4, 0.6, and 1.0 kg ae ha−1. The defunct 2003 National Turfgrass Evaluation Program fineleaf fescue variety trial at the Turfgrass Research Center in Blacksburg, VA, provided main plots on which glyphosate treatments were randomized independently on May 16, 2011, and June 26, 2013. Hard (HF) and sheep fescues (SF) were the most tolerant to glyphosate, followed by strong creeping red fescues (STC) and slender creeping red fescues (SLC). The most sensitive species was Chewings fescue (CH), most varieties of which were injured 50% to 65% per kilogram of glyphosate at 2 wk after treatment (WAT). At 8 WAT, 12 of 14 CH varieties were injured over 30% per kilogram of glyphosate, but predicted injury and normalized difference vegetation index (NDVI) of all varieties were acceptable at a more typical 0.5 to 0.7 kg ha−1glyphosate rate. Nontreated seed head density of CH varieties ranged from 87 and 126 seed heads m−2at 8 WAT compared with 2.8 to 42 seed heads m−2from HF varieties. Glyphosate at 0.15 to 0.5 kg ha−1eliminated 90% of seed heads regardless of fineleaf fescue variety. These data suggest that all fineleaf fescue varieties are inherently tolerant of glyphosate at rates at or below approximately 0.7 kg ha−1, but can be generally separated from most to least tolerant in the following order: HF, SF, STC, SLC, and CH.