Hop Response to Glufosinate-Based Spring Pruning and Implications for Crop and Weed Management

Spring pruning of hops (Humulus lupulus L.) is a critical practice to reduce foliar disease inoculum and control weeds, thereby supporting more profitable hop production. Although paraquat and carfentrazone have been used for early spring pruning, increasing regulatory restrictions on paraquat and the limited efficacy of weed control offered by carfentrazone highlight the need for alternative solutions. This study evaluated glufosinate, a non-selective postemergence herbicide, during spring pruning of hop plants. Four field studies were conducted between 2022 and 2024 in experimental and commercial hop yards located in Washington and Oregon. Treatments included glufosinate applied at 1,150 g ai ha⁻¹ and 2,295 g ai ha⁻¹, either as a single or two sequential applications, compared to carfentrazone (35 g ai ha⁻¹) and a nontreated control. Sequential applications were made 14 days apart. Across all site years, glufosinate consistently provided superior hop basal shoot control, with 14 and 28 days after initial treatment (DAIT) control ranging from 50% to 96% and 34% to 96%, respectively. In contrast, carfentrazone resulted in lower control levels (36%–50% at 14 DAIT; 8%–34% at 28 DAIT). Glufosinate effectively controlled kochia (84%–93% at 28 DAIT), outperforming carfentrazone (<25%). In addition to improved weed and hop shoot control, no negative effects were observed in hop plant height or bine fresh weight at harvest, except in one-year-old hops. These findings support that glufosinate is safe and effective for spring pruning in mature hops, though crop age should be considered to ensure crop safety.