Featured image: Example of bacterial bulb rot. Photo from Lindsey du Toit. Additional photos provided below. Please make note of the descriptions associated with all photos.
By Stuart Reitz
Director
Oregon State University Malheur Extension
Ontario, Oregon
The Onion Session at the 2024 Pacific Northwest Vegetable Association Annual Meeting included a full day of twelve presentations on America’s favorite bulb crop with pest management topics interwoven with other topics of concern for PNW growers.
Michael Locati and Jason Brown started the day by providing an update on the activities of the Columbia Basin Onion Research Committee and the importance of the research that it funds. The Committee is composed of growers and allied industry partners who make voluntary contributions to support research projects and are then leveraged by scientists to help acquire additional state and federal research grants. Michael and Jason encouraged more onion industry members in the Columbia Basin to participate in the committee.
Gina Greenway, from Greenway Research, gave an update on farm economics and the outlook for the 2025 growing season. One of Gina’s takeaways is to pay attention to the seasonality of price changes for inputs like fuel and fertilizer. For example, fuel prices typically decline in the fall only to rebound the following spring and summer, which means it can be advantageous to time purchases even though the overall price trends for certain commodities may still be on the rise.
Carrie Wohleb from WSU introduced the pest management talks by taking attendees on a “CSI” investigation of “what is wrong with my onions?” or steps to take in diagnosing problems in the field. Oftentimes, many problems – from diseases to environmental stresses – can appear similar. Therefore, it is critical to pay attention to a wide range of evidence to help distinguish among causes of problems.
One of the most important problems facing onion growers is bulb rots. Lindsey du Toit, WSU, gave an overview of bacterial problems that have been the focus of the “Stop the Rot” project that she is leading. Different complexes of bacterial diseases are found in different production regions, but du Toit emphasized that regardless of the types of bacteria growers may have, they cannot spray their way out of the problem. Therefore, it is critical for growers to try to minimize infections in the first place. Some of these steps include not overfertilizing or over-irrigating their crop, both of which significantly increase risks for bulb rots, and allowing onions to cure thoroughly before topping. More information on the project is available at https://alliumnet.com/stop-the-rot/.
Alan Schreiber, Agriculture Development Group, reviewed his research on nematode management. Nematodes are a widespread, but perhaps underappreciated, pest of onions. According to Schreiber, two of the current standard treatments, Telone fumigant and soil-applied Vydate, face increasing limitations on their use from buyer requirements, regulatory restrictions, and cost. In Schreiber’s research, NemaClean, MeloCon, and Onira have provided encouraging results, either on their own or in concert with Vydate. Developing management plans that feature such novel products could reduce growers’ environmental footprint and Environmental Impact Quotient (EIQ).
Mike Thornton, University of Idaho, summarized his recent research on why onions in the inner row of drip irrigated beds tend to be smaller than ones in the outer row. There are probably multiple factors, including poorer seed-to-soil contact, cooler early-season soil temperatures, and lower soil nitrogen availability in the inner row that contribute to reduced plant size in the inner row. Thornton also discussed his research on managing pink root in onions. Over many years of research, Thornton has found that soil-applied fungicides in concert with either chloropicrin or metam as a fumigant can substantially reduce the severity of pink root, especially for metam, as it is not as effective against pink root as chloropicrin. At the end of what would be Mike’s last PNVA presentation, association president Jim Zahand presented him with a plaque to honor Mike’s many years of service to the PNVA and the onion industry. Mike will be retiring from the University of Idaho in February.
Figure 1. Similar appearing stand loss problems caused by overly acidic soil (left), Rhizoctonia damping off (upper right), and stubby root nematodes (lower right). Photos provided by Carrie Wohleb.
Figure 2. Examples of bacterial bulb rots. Photos from Lindsey du Toit
Figure 3. Stunted onions on the inner row of drip-irrigated onions. Photo from Mike Thornton.
Figure 4. Severe pink root in onion. Photo from Mike Thornton.
