Evaluation of amino acid–inhibiting herbicide mixtures for hair fescue (Festuca filiformis) management in lowbush blueberry

Abstract

Hair fescue is a perennial grass weed in lowbush blueberry fields that forms dense sods and reduces yield. Growers rely on preemergence (PRE) pronamide applications and postemergence (POST) applications of the group 2 herbicides foramsulfuron and nicosulfuron + rimsulfuron for hair fescue management due to natural tolerance or resistance of this grass to other currently registered herbicides. This causes repeated application of group 2 herbicides, which is compounded by the recent registration of flazasulfuron for POST hair fescue suppression in lowbush blueberry. Mixtures of group 2 herbicides with the amino acid-inhibiting herbicides glyphosate (Group 9) and glufosinate (Group 10), however, can improve weed control and may provide mixtures to delay herbicide resistance development. This research utilized a factorial arrangement of group 2 herbicide (none, foramsulfuron [35 g ai ha-1], nicosulfuron + rimsulfuron [13 + 13 g ai ha-1], flazasulfuron [50 g ai ha-1]) and mixture (none, glyphosate [902 g ae ha-1], and glufosinate [750 g ai ha-1]) to identify possible mixtures that improve weed control and delay resistance development. Herbicides were applied in spring non-bearing year, fall bearing year, and fall non-bearing year, with each application timing conducted as a separate experiment. Foramsulfuron and nicosulfuron + rimsulfuron were not effective as fall applications and spring applications of these herbicides with glyphosate or glufosinate improved hair fescue suppression. Glyphosate and glufosinate were more effective as fall rather than spring applications. Flazasulfuron was effective across all application timings, though mixture with glufosinate generally improved hair fescue suppression. Flazasulfuron + glufosinate is tentatively recommended as an effective mixture for spring non-bearing and fall bearing year hair fescue management in lowbush blueberry.

Evaluation of dichlobenil for hair fescue (Festuca filiformis Pourr.) management in wild blueberry (Vaccinium angustifolium Ait.)

“…acid), foramsulfuron, and flazasulfuron (White, 2022;White & Graham, 2021;White & Kumar, 2017;Zhang et al, 2018), these herbicides do not reduce living tuft density to the same extent as pronamide and dichlobenil as demonstrated by this study. As such, dichlobenil is an important herbicide for future sustainability of hair fescue management due to similar efficacy as pronamide via a different site of action.…”

“…Lack of seed dormancy, rapid seedling emergence following the seed rain, and transient seed banks are considered high‐risk traits for evolution of herbicide resistance (Kumar et al., 2019). Although wild blueberry growers can suppress hair fescue with pronamide alternatives such as clethodim (2‐[(E)‐ N ‐[(E)−3‐chloroprop‐2‐enoxy]‐ C ‐ethylcarbonimidoyl]−5‐(2‐ethylsulfanylpropyl)−3‐hydroxycyclohex‐2‐en‐1‐one), glufosinate (2‐amino‐4‐[hydroxy(methyl)phosphoryl]butanoic acid), foramsulfuron, and flazasulfuron (White, 2022; White & Graham, 2021; White & Kumar, 2017; Zhang et al., 2018), these herbicides do not reduce living tuft density to the same extent as pronamide and dichlobenil as demonstrated by this study. As such, dichlobenil is an important herbicide for future sustainability of hair fescue management due to similar efficacy as pronamide via a different site of action.…”