OSU Field Research Targets Key Challenges For Organic Vegetable Growers

Growers moved from potato plots to tomato trials at Oregon State University’s Lewis-Brown Horticulture Farm, stopping along the way to examine plants, ask questions and hear how researchers are tackling production challenges in organic vegetable systems.

The Sept. 14 Organic Vegetable Field Day, presented by the OSU Organic Agriculture Program and Vegetable Breeding Program in partnership with Oregon Tilth, brought growers together with researchers working on symphylans, tomato breeding, cover crops, pulses and other projects.

The Organic Agriculture Program is in the Center for Resilient Agriculture and Food Systems in the College of Agricultural Sciences.

The event gave participants a chance to walk through research plots, hear preliminary findings and discuss how the work might translate to organic farms.

Tracking a difficult pest
Symphylans are tiny, soil-dwelling arthropods that feed on plant roots and seedlings. Their populations can be concentrated in patches and shift with soil conditions and crop rotations, making them difficult to monitor and manage.

Nick Andrews, professor of practice and Extension organic vegetable specialist with OSU, said vegetable growers have been asking him about symphylans since he began working for OSU about two decades ago.

Earlier research by then-OSU post-doctoral researcher Jon Umble showed that growers could monitor symphylans more efficiently using potato bait rather than relying on bulk soil sampling. It also found that potatoes grown in rotation can sharply reduce symphylan populations.

At the field day, Sai Mahulkar, a faculty research assistant in the Organic Agriculture Program, demonstrated the baiting method as Andrews explained the process. They begin by looking for suspected hot spots, often where plants are stunted.

Pieces of potato are placed cut-side down against moist soil and covered with a container. Researchers typically set 12 baits in an area and return after two days to count symphylans on the potato and immediately beneath it.

Timing matters. Andrews said sampling works best when soils are moist and daytime highs are roughly 55 to 75 degrees, generally in spring. When unirrigated soil becomes hot and dry, symphylans move deeper into the soil and become harder to detect.

Monitoring conducted on cooperating farms has shown how widely populations can vary. Some sites had few or no symphylans, while others had dozens. At one site, researchers counted 348 from 12 potato baits after two days.

That information can help growers decide what to plant next. Researchers are developing an integrated approach built around monitoring, crop rotations, suppressive crops and biopesticides that can be used in organic production.

Navneet Kaur, an Extension entomologist in OSU’s Department of Crop and Soil Science, said the goal is to identify approaches that reduce symphylan populations while fitting organic production systems.

Her program has tested several biopesticides. A spinosad-based bait called Seduce showed promising suppression in sugar beet and organic spinach seed trials, while other products produced mixed or inconclusive results. Additional products are being evaluated.

Crops that suppress symphylans
The potato plots addressed another practical question. If potatoes are primarily to suppress symphylans and are terminated early, will they become a weed problem for the next crop?

Researchers planted ‘Russet Burbank’ potatoes in 2025 and terminated them eight, 11 and 14 weeks after planting. The following season, they tracked volunteer potato plants emerging from tubers left behind.

Plots terminated after eight weeks produced few volunteers, while later termination resulted in substantially more. Volunteer potatoes were most vigorous when the previous plants were terminated 14 weeks after planting. Andrews said that creates a trade-off for growers who might plant potatoes primarily for symphylan suppression rather than as a harvested crop.

Earlier termination could provide suppression while reducing the risk that volunteer potatoes become a weed problem in the next crop.

Researchers are also trying to understand why potatoes suppress the pest.

Kaur and graduate student Aoibheann Kavanagh are studying glycoalkaloids, naturally occurring plant defense compounds that may be toxic to symphylans. Their greenhouse work has expanded beyond potatoes to look for other crops that might provide similar suppression.

Habanero peppers have been among the most promising so far, producing suppression comparable to potatoes. Ashwagandha has also performed well, while some tomato types have shown lower levels of suppression. Researchers are continuing to test plants and analyze their roots to determine which compounds may be responsible.

Nearby, another set of plots illustrated a different goal for organic growers.

Jim Myers, professor emeritus and retired vegetable breeder in the Department of Horticulture, led participants through Tomato Organic Management and Improvement tomato trials. The national project, known by its acronym TOMI, has operated for about a decade and includes researchers in several states.

The work is aimed at developing tomato varieties suited to organic production, with traits such as multiple disease resistance, productivity, flavor and other quality characteristics. Oregon trials also include biological control research on cooperating farms, including Goodfoot Farm in Philomath.

Growers help shape the work
Beth Hoinacki of Goodfoot Farm attended the field day and said it goes beyond receiving research results. Growers also have an opportunity to tell researchers what they are seeing and which questions deserve attention.

“We play different roles in supporting organic agriculture,” Hoinacki said. “The field days provide an opportunity to help do that.”

That exchange extended across several shorter research updates during the afternoon.

Andrews introduced a cover crop species selector developed through the Western Cover Crops Council. Users enter their farm location and their top objectives, such as nitrogen, weed control, erosion reduction or pollinator habitat. The online tool draws on soil and climate information to suggest species.

Additional tools under development include calculators for cover crop seeding rates, economics and nitrogen contributions. Shannon Cappellazzi, assistant professor of practice and Extension soil health specialist, is also expanding Oregon cover crop variety trials to multiple locations and working more closely with national cover crop breeding and variety-testing efforts.

Andrews also described research evaluating common vetch for winter hardiness, biomass and seed production. He has screened about 113 lines from the USDA germplasm collection along with Oregon-grown landraces.

One promising variety, ‘AU Olympic,’ survived a very cold winter during its development. Researchers have begun increasing a limited supply of breeder seed.

Brigid Meints, assistant professor of practice and Extension organic grains and pulses specialist, and Lucas Nebert, assistant professor of practice and Extension organic seed and planting stock specialist, shared a separate irrigation study involving cowpeas, tepary beans, chickpeas and lentils.

Taken together, the projects give organic growers more information to weigh as they make decisions about pests, rotations, varieties, irrigation and soil management.

The field day also gives researchers direct feedback from the people who may eventually use the results, helping keep the work tied to problems farmers are encountering in their fields.

Hoinacki said that exchange is one of the event’s strengths.

“I think we all learn from each other,” she said. “We bring different perspectives that are important.”