Evaluation of acetolactate synthase/acetohydroxyacid synthase – inhibiting herbicide spot applications and mesotrione tank mixtures for narrow-leaved goldenrod management in lowbush blueberry

Abstract

Narrow-leaved goldenrod is a common creeping herbaceous perennial weed in lowbush blueberry that is difficult to manage due to limited control from pre-emergence hexazinone applications and incomplete control from post-emergence mesotrione applications. The objectives of this research were to (1) evaluate a range of summer and fall non-bearing year acetolactate synthase/ acetohydroxyacid synthase (ALS/AHAS) – inhibiting herbicide spot applications for narrow-leaved goldenrod control, and (2) evaluate broadcast applications of mesotrione applied alone or in tank mixture with foramsulfuron, nicosulfuron + rimsulfuron, flazasulfuron, and clopyralid for crop tolerance and management of narrow-leaved goldenrod in lowbush blueberry. Summer non-bearing year spot applications of glyphosate and flazasulfuron caused >90% visual injury to narrow-leaved goldenrod and reduced both non-bearing and bearing year shoot density. Spot applications of tribenuron methyl, foramsulfuron, nicosulfuron + rimsulfuron, halosulfuron, and pyroxsulam caused variable injury and did not consistently reduce narrow-leaved goldenrod shoot density. Results were similar in the fall non-bearing year experiment and they indicate that flazasulfuron could be used as an alternative to glyphosate for spot applications to narrow-leaved goldenrod due to lower crop injury from this herbicide relative to glyphosate. Broadcast mesotrione applications injured narrow-leaved goldenrod but did not reduce shoot density. Broadcast foramsulfuron, nicosulfuron + rimsulfuron, and clopyralid applications caused <60% narrow-leaved goldenrod injury and did not reduce shoot density. Tank mixture of these herbicides with mesotrione did not improve narrow-leaved goldenrod control. Broadcast flazasulfuron applications caused >60% visual injury to narrow-leaved goldenrod and reduced non-bearing year and bearing year shoot density. Flazasulfuron efficacy was reduced when applied in tank mixture with mesotrione.