Viticulture - Advances in Pest Management Session

Cody Copp* | Mingchang Liao | John Bouranis

Kaolin Clay Reduces Fruit Sunburn and Leafhopper Abundance While Minimally Affecting Vine Water Stress in Oregon

Cody Copp,* Mingchang Liao, and John Bouranis

*Oregon State University and Southern Oregon Research and Extension Center, 569 Hanley Road, Central Point, OR, 97502, cody.copp@oregonstate.edu

Kaolin clay can be used to manage abiotic stress and pests for horticultural crops like winegrapes. The changing climate in Oregon and the greater Pacific Northwest demands more tools to adapt particularly susceptible perennial systems like vineyards. Multiple field experiments were conducted in northeastern Oregon between 2022 and 2024 to measure the effect of kaolin on vine water stress, fruit sunburn, and leafhopper populations. Kaolin was applied to Syrah at 0, 11, 22, and 45 kg/ha and vine stress responses were observed. Kaolin was applied to Syrah, Tempranillo, and Mourvèdre prior to postveraison (2023) and preveraison (2024) multiday heat events (T_air >40°C) to evaluate the effect on fruit sunburn symptoms. Western grape leafhopper populations were monitored in an organic Cabernet Sauvignon vineyard with some kaolin-treated blocks. In 2022, the Syrah vines treated with 45 kg/ha had 25% higher stomatal conductance at moderate leaf water potential values (> -1.4 MPa); leaf water potential was unaffected in 2023 and 2024. Leaf temperature trended lower and stomatal conductance trended higher, mediated by increased leaf reflectance scalar with kaolin application rate. Kaolin application prior to pre- and postveraison heat events reduced fruit sunburn symptoms. Treated clusters had up to 85% fewer shriveled berries, up to 34% fewer berries with sunburn browning, up to 11% fewer necrotic berries, and up to 25% higher anthocyanin concentration. Kaolin application at 22 kg/ha reduced the abundance of leafhopper nymphs on leaves but did not reduce the number of adults trapped with sticky cards. The second-generation peak nymph populations were 54% and 80% lower in kaolin-treated blocks in 2023 and 2024. Ultimately, kaolin clay is an effective tool for grapegrowers to mitigate specific abiotic (e.g., sunburn, water) and biotic (e.g., insect) stresses and its use should be tailored to specific climatic and environmental conditions.

Funding Support: Agricultural Research Foundation Oregon Wine Research Institute ETS Laboratories

Tian Tian* | Mandeep Riar

Using Organic Herbicides and Steam for Weed Control in California Vineyards

Tian Tian* and Mandeep Riar

*University of California Cooperative Extension, 1031 S Mt Vernon Ave, Bakersfield, CA, 93307, titian@ucanr.edu

Organic growers in the San Joaquin Valley, California rely on both mechanical methods and plant-based herbicides for weed management in vineyards. Interests in alternative methods, such as steam and electric discharge weeders, keep increasing in recent years. In 2023 and 2024, we evaluated the efficacy of organic herbicides, a rubber finger weeder, and a steam weeder for under-vine weed control in three table grape vineyards in Kern County, CA. Our study examined three herbicides: Suppress (caprylic acid and capric acid), WeedZap (clove oil and cinnamon oil), and Perish (eugenol and thyme oil). The predominant weed species included prickly lettuce (Lactuca serriola L.), hairy fleabane (Erigeron bonariensis L.), horseweed (Erigeron canadensis L.), purple nutsedge (Cyperus rotundus L.), silverleaf nightshade (Solanum elaeagnifolium Cav.), crabgrass (Digitaria sanguinalis L.), fiddlenecks (Amsinckia spp.), and common lambsquarters (Chenopodium album L.). Across 2 yr, the steam weeder demonstrated comparable weed control efficacy to Suppress when applied at a high rate. With four applications between April and October, both methods reduced weed coverage by ~80%. Both methods proved more effective against broadleaf weeds than grasses. In contrast, WeedZap and Perish, even when applied at high label rates, reduced weed coverage by ~35% after four applications, indicating lower efficacy than Suppress, a widely used herbicide in organic systems. The rubber finger weeder effectively controlled small weeds (<10 cm) in vineyards with coarse-textured soils, yet had limited effectiveness against larger weeds, especially those with deep root systems. Overall, our findings suggest that steam weeding is a viable and cost-effective alternative to herbicide application in organic vineyard systems. The success of the rubber finger weeder depends significantly on weed growth stages and soil texture within the vineyard. Future studies aim to assess the effectiveness of electric discharge weeders in comparison to steam and finger weeders.

Funding Support: California Table Grape Commission

Michelle Moyer* | Katherine East | Inga Zasada

Long-Term Effects of Preplant Fumigation and Rootstocks on Northern Root-Knot Nematode Population Dynamics

Michelle Moyer,* Katherine East, and Inga Zasada

*Washington State University, 24106 North Bunn Rd, WSU Prosser IAREC, Prosser, WA, 99350, michelle.moyer@wsu.edu

This work followed Meloidogyne hapla (Northern root-knot nematode) population dynamics over a 10-yr period in a commercial vineyard where pre-plant fumigation and the use of rootstocks were adopted to mitigate nematode-induced vine decline. The rootstocks 101-14 MGT, 1103P, Harmony, and Teleki 5C, and own-rooted Vitis vinifera controls were planted in plots that were fumigated (metam sodium), nonfumigated, or nonfumigated + inoculated with additional M. hapla at planting. By the second year after establishment, the fumigation effect was no longer detectable. By the fifth year, all evaluated “resistant” rootstocks supported similar nematode densities as own-rooted vines. In highly susceptible own-rooted vines, non-fumigated plots supported higher nematode densities early in establishment; however, population densities did not significantly increase over the 10-yr study. In fumigated plots, nematode population densities rebounded to pre-plant densities ~3 yr postfumigation and subsequently entered a recurring boom-and-bust cycle with an ~3 yr periodicity. The non-fumigated + inoculated plots immediately exhibited this cyclical pattern. Chronic nematode buildup on own-rooted vines exceeded that observed on rootstocks (p < 0.0001); Teleki 5C and 1103P maintained slower buildup of M. hapla densities compared to 101-14 MGT and Harmony. Over the long term, improved vine vegetative growth was maintained when using rootstocks relative to own-rooted vines, averaging an ~20% increase in pruning weights. This work demonstrates that nematode population densities in vineyards are variable both within and between seasons, and that population disruptions—whether through fumigation or the introduction of additional individuals—can trigger large population fluctuations. When populations are not disturbed, a natural carrying capacity appears to exist, even in the presence of a susceptible host. Rootstocks were an effective long-term management option to mitigate symptoms of nematode-induced vine decline by maintaining more predictable vine vegetative growth and avoiding the major population swings observed in own-rooted vines.

Funding Support: The Washington State Grape and Wine Research Program, supported by Washington State University, Auction of Washington Wines and all Washington State wine grape growers and wineries through the Washington State Wine Commission; The USDA National Institute of Food and Agriculture, Hatch project 7005262.

From Hyperspectral Pixels to Vineyard Decisions: Lessons from the AVIRIS4Acres-NY Campaign

Kaitlin Gold,* Dana Chadwick, Yu Jiang, Phil Broderick, Shivranjani Baruah, Manushi Trivedi, Henry Frye, Phil Townsend, Yiyuan Lin, Timothy Williams, David Combs, Nicholas Regnier, Niko Carvajal Janke, Lorenzo Pippi, Hans Walter-Peterson, Terry Bates, Jennifer Russo, Yun Yang, Madeline Oravec, Jason Londo, Faith Twinamaani, Lance Cadle-Davidson, Alison Bredder, Michael Humber, and Alyssa Whitcraft

*Cornell University, 15 Castle Creek Drive, Geneva, NY, 14456, kg557@cornell.edu

High-resolution airborne visible-shortwave infrared (VSWIR) imaging spectroscopy is emerging as a practical way to translate research-grade sensing into vineyard-scale decision support, but few campaigns have been designed around the spatial, temporal, and communication needs of commercial management. In July 2025, the AVIRIS4Acres-NY campaign acquired 0.5 to 1.25 m narrow-band hyperspectral imagery over research and commercial vineyards in upstate New York, co-designed with growers and extension partners through stakeholder listening sessions to prioritize actionable products. Near-real-time, cloud-delivered Level-2 outputs were generated during flight and shared through an interactive viewer, enabling rapid evaluation of canopy condition, within-block vigor variability, and stress “hotspots” relevant to targeted scouting and intervention. We present an end-to-end workflow that links calibration/validation protocols and coincident leaf and canopy sampling for trait reference libraries; initial retrievals of foliar traits associated with canopy function and stress; preliminary AI/ML approaches for early grapevine disease detection; and an extension-integrated engagement model that supports real-time ground truthing and iterative refinement of maps. Results demonstrate a feasible pathway for converting hyperspectral imagery into vineyard management intelligence, supporting prioritization of scouting, identification of spatial patterns consistent with nutrient or water stress, and early detection research while also de-risking future satellite applications by informing band selection and processing architectures. This campaign provides a replicable template for aligning advanced airborne sensing with viticulture stakeholder needs and for accelerating development of decision-ready tools for regional early-warning systems.

Funding Support: NASA Acres Domestic Agriculture Research Consortium

3:15 pm – 3:35 pm	Kaolin Clay Reduces Fruit Sunburn and Leafhopper Abundance While Minimally Affecting Vine Water Stress in Oregon Cody Copp, Oregon State University, Central Point
3:35 pm – 3:55 pm	Using Organic Herbicides and Steam for Weed Control in California Vineyards Tian Tian, University of California Cooperative Extension, Kern County
3:55 pm – 4:15 pm	Long-Term Effects of Preplant Fumigation and Rootstocks on Northern Root-knot Nematode Population Dynamics Michelle Moyer, Washington State University, Prosser
4:15 pm – 4:35 pm	From Hyperspectral Pixels to Vineyard Decisions: Lessons from the AVIRIS4Acres-NY Campaign Kaitlin Gold, Cornell University, New York

Viticulture – Advances in Pest Management Session

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