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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Production and Genetic Improvement Research Unit » Research » Research Project #441011

Research Project: Expanding Weed Control Options for Cranberry Growers

Location: Horticultural Crops Production and Genetic Improvement Research Unit

Project Number: 2072-21000-055-021-G
Project Type: Grant

Start Date: Sep 1, 2021
End Date: Oct 31, 2024

Objective 1. To assess cranberry tolerance to new herbicides using chemigation to extend weed control; Objective 2. Evaluating the efficacy of new systemic herbicides to control sheep sorrel and other perennial weeds in cranberry using wiper application or saturated steam for targeted weed control.

Objective 1: Growers have identified sheep sorrel, slough sedge, yellow loosestrife, creeping bentgrass, moss, among others as problematic weeds in cranberry. We have identified two phenological stages in cranberry, dormant and pre-bloom, to evaluate new herbicides. Trial herbicides were selected based on consultation with manufacturers, the IR-4 program, and colleagues based in the eastern US. For the dormant application, we selected tiafenacil (Reviton), pronamide (Kerb SC), and indaziflam (Alion). Treatments will be applied in early spring (March-April) at two rates: the expected field rate based on other crops and twice that rate. The experiment will be organized as a randomized complete block design with four replicates. For the early spring chemigation study we have selected sulfentrazone (Zeus), pyroxasulfone + flumioxazin (Fierce), and oxyfluorfen + penoxsulam (Pindar GT). Treatments will be applied at the dormant and pre-bloom stages, and at two rates per herbicide: the expected field rate, and twice that rate. Within 6 hours after treatment, plots will be irrigated with 0.5 acre-inch to rinse any product from crop foliage. Besançon et al. (in-press) has shown this method to be safe in cranberry. The experiment will be organized as a three-factor factorial with application timing, herbicide, and herbicide rate as the three factors. Objective 2: Sponge wiper application is widely used in commercial cranberry fields with glyphosate and clopyralid. We have identified a new herbicide, florpyrauxifen-benzyl, a synthetic auxin with activity in grasses, sedges, and broadleaves. The low toxicity of florpyrauxifen-benzyl exempts it from a tolerance requirement, making it a right candidate for registration (EPA 2019). Preliminary tests indicated that florpyrauxifen is not safe when applied over-the-top of actively grown cranberry; however, its systemic mode of action makes it a right candidate for sponge-wiper applications. We propose to test florpyrauxifen against sheep sorrel, yellow loosestrife, and slough sedge. Weeds will be grown in containers and treated at two different growth stages – 2 to 4 inches tall and 8 to 12 inches tall. The first test will identify the herbicide concentration (2% to 30% concentration) required to control these plants. Once an effective concentration is identified, a second study will compare the field efficacy of the wiper application of florpyrauxifen, clopyralid, clopyralid + florpyrauxifen to a string weeder (reference) and saturated steam. Steam will be generated by an SW900 (Weed Technics) and applied using a hand-held unit to target the weed. The experiments will be organized and randomized as a complete block design with four replicates and repeated.