Non Technical Summary
This is an ARDP single-function research project focused on Plant Protection Tools and Tactics. This project will consider the performance, safety, and economic sustainability of electric weed control (EWC) as an herbicide resistance-management strategy in hazelnut orchards. Herbicide resistance is the greatest weed management challenge identified in multiple commodities. In Oregon hazelnut orchards, there are confirmed cases of resistance and multiple resistances to postemergence and more recently preemergence herbicides, jeopardizing herbicide mixtures and rotations as management tools. EWC can fundamentally change weed management in hazelnut and mitigate herbicide resistances. EWC is the only effective non-chemical weed control tool because tillage is limited in hazelnut, and mowing is ineffective. Our approach includes field research in collaboration with growers and on university farms. We have established four objectives to advance the integration of EWC in hazelnut orchards. (i) Development of weed-specific recommendations for EWC in short-term studies in commercial fields. (ii) Quantification of the effect of foliar-applied electrical weed control (EWC) on weed densities, herbicide use, and gross returns under different weed management approaches in hazelnuts. (iii) Continued evaluation of the effects of EWC applied over multiple years on hazelnut growth and yield. (iv) Develop soil-applied EWC recommendations to manage preemergent weeds In partnership with the private sector. Expected outcomes include reducing reliance on herbicides, mitigating herbicide resistance management costs, and reducing human exposure to chemicals. Our findings will apply to a wide range of perennial crops.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
216	1210	1140	100%

Knowledge Area
216 - Integrated Pest Management Systems;

Subject Of Investigation
1210 - Filbert;

Field Of Science
1140 - Weed science;

Goals / Objectives
Objective 1: Develop weed-specific recommendations for EWC. Determine the effectiveness of EWC technologies over weed species in short-term studies.Objective 2: Quantify the effect of EWC on weed densities, herbicide use, and gross return under different weed management approaches. (research-oriented)Objective 3: Monitor the long-term effect of EWC on hazelnut growth and yield.Objective 4: Develop a soil-applied EWC method to manage weeds in preemergence.

Project Methods
Objective 1: Develop weed-specific recommendations for EWC. EWC depends on its efficacy and operation costs. To develop a cost-effective EWC tactic, we must identify optimal performance under various environmental and operational conditions. We anticipate conducting six replicated studies annually, lasting nine weeks each. These will be initiated in fall-winter, spring, and summer. Each study will include three operation speeds (one to six km h-1) and one to three operations performed at three weeks intervals. The experiment will be organized as a two-factor factorial organized as a randomized complete block design. A nontreated check and grower's standard weed control (e.g., glufosinate) will be included for comparison. We will record data describing operation parameters (speed, voltage, amperage), soil type, temperature, gravimetric soil moisture, and weed density by species, size, and coverage following methods proposed previously. Weed response to electrical damage will be visually quantified on a rating scale ranging from 0% (no injury) to 100% (weed death) every seven days. Above-ground weed biomass will be collected, separated into reproductive and non-reproductive structures, and weighted.Objective 2: Quantify the effect of EWC on weed densities, herbicide use, and gross return under different weed management approaches.A long-term field study will be initiated at the OSU Lewis Brown Research Farm in Corvallis, OR. The orchard will be planted with a commercial cultivar at 3 by 6 m spacing, irrigated, and trained as a single-trunk tree following standard production practices. The following treatments will be compared: 1) weedy check, 2) weed-free check, 3) standard practices (pre-and post-emergence herbicides) plus mowing, 4) electrical weed control, and 5) standard practice plus electrical weed control. Treatments will be applied in winter, spring, summer, and fall. Retreatment will be performed as needed to minimize weed seed production. Treatments will be arranged in a randomized complete block design with five replicates. Trunk cross-sectional area and canopy volume will be estimated by measuring plant height and diameter Yield will be recorded when trees reach bearing age. Weeds will be identified at the species level. Weed control per species will be assessed monthly with visual estimates. Weed cover and weed presence will be recorded at three sampling times per year, including late winter, mid-summer, and early fall. A grid with 25 intersecting points will be mounted on a 0.25 m-2 quadrat and measured four times per plot per sampling time in a regular distribution pattern (Nkoa et al. 2015). All expenses for purchased materials will be recorded. The labor required for all activities will be recorded to the nearest second and differentiated between the machine operator and hand labor. We will calculate machinery costs using an online tool.using a mixed model. Contrasts will be used to compare EWC to the standard method.Objective 3: Monitoring the long-term effect of EWC on hazelnut growth and yield.This objective continues a study initiated in 2021 with the previous NIFA CPPM grant award 2020-70006-32982. The current work aims to monitor the EWC effect on hazelnut growth and yield when applied to hazelnut suckers. The orchard was planted with two cultivars of economic importance in Oregon, 'Yamhill' and 'Wepster,' with drip irrigation. The treatments include (1) nontreated weed-free check, (2) power harrow as a reference, (3) EWC at a high rate (0.4 km h-1) without suckers; (4) EWC at a low rate (1.25 km h-1) without suckers, (5) EWC at a high rate (0.4 km h-1) with suckers, and (6) EWC at a low rate (1.25 km h-1) with suckers. Treatments will be applied to the same plots four times a year. The field is weed-free with moving, hand weeding, and spot treatments. We will monitor tree trunk growth, sucker shoot elongation, canopy volume, yield, and leaf nutrient analysis to monitor the long-term effects like methods described in objective 2. The experimental design is a two-factor randomized complete block with six replicates. Hazelnut cultivar and the treatments are the second factors.Objective 4: Develop a soil-applied EWC method of managing weeds in preemergence. (research-oriented)In this objective, we will use a commercially available unit to apply a pulse electric field (PEF) to the soil to kill weed seeds before they emerge. PEF has been shown to reduce the germination of yellow nutsedge by 75% after a 40 s treatment at 14 kV. The Direct Energy System (DES, Lisi Global, Inc.) unit delivers energy via pins or electrodes inserted into the soil (Figure 6). Pin spacing and length are adjusted according to the volume of soil to be treated. The DES unit is autonomous, battery-powered, and capable of delivering electricity while stationary or moving up to 8 km h-1. The application apparatus uses pins 1.27 cm wide mounted on a 1.2 m long bar. Electric pulses are delivered at the soil surface and up to a maximum depth of 25 cm. A field study will compare PEF effects against naturally occurring weed species and newly planted hazelnut. The orchard will be planted in a Malabon silt loam soil at the OSU Corvallis Research Farm. The electric pulse will be applied to a depth of 2 cm. PEF treatments will include three levels of electric field strength designated as low (20 kV.mm-1), medium (50 kV.mm-1), or high energy (200 kV.mm-1). Pulse frequency, width, and duration of treatment (travel speed) will be manipulated to achieve three energy inputs ranging from as low as 20 J.cm-3 to as high as 150 J.cm-3. A non-treated control and a weed-free treatment will be included as references. Treatments will be applied twice yearly to the same plots in early spring and early fall for two years. The number and width of pulses will be recorded. These data will inform the energy required to provide adequate weed control without disrupting hazelnut growth.