Strategies and methods to manage major insects and diseases of onion

Onions are susceptible to a range of pests and diseases, both in the field and during storage, which can significantly diminish their yield and quality. Among the most pressing challenges for sustainable onion production in Norway are the onion fly and Fusarium basal rot. QualityOnion project aims to mitigate yield and quality losses in onions through comprehensive strategies that include detection, monitoring, warning systems, and strategic control of fusarium basal rot and onion fly. Key objectives include Developing a prototype trap for monitoring onion fly populations, alongside the adaptation of a German onion fly simulation model to better suit Norwegian conditions; Identifying Fusarium species responsible for fusarium rot in Norwegian onions; Developing molecular methods for identifying onion flies and for detecting and quantifying Fusarium in both onions and soil. Evaluating the effectiveness of various low-risk fungicides, biostimulants, microbial biological control agents, basic substances, and traditional chemical fungicides to combat the different Fusarium species affecting onions in Norway and determine the interaction between onion mites and fusarium. The project is progressing according to plans. Blue traps with and without the odour have been tested in different onion fields during the two consecutive growing seasons (2024-2025) to develop and optimize the trap for onion fly monitoring. In addition, the onion flies collected from the traps are being utilized to refine the simulation model for onion fly population dynamics and may also be used to develop a method for fast molecular-ID of onion fly. Experiments in greenhouses and fields are underway to evaluate alternative ways to manage Fusarium basal rot. Infected onions have been collected from across Norway, and the Fusarium species are being identified. Molecular detection methods are also being developed. Experiment testing the interactive effects of Fusarium basal rot and bulb mite on onion growth and mortality has been completed.

Onion fly and Fusarium basal rot represent major threats for sustainable Norwegian onion production. There are substantial gaps in our knowledge regarding these pests such as which Fusarium species infect onions in Norway, what are the main sources of Fusarium inoculum, and how onion fly prevalence is changing through the growing season. As the development of integrated pest management (IPM) strategies relies heavily on an understanding of pest biology, ecology, epidemiology, and environmental factors conducive to epidemic development, the knowledge gaps related to onion fly and Fusarium spp. hamper researchers’ and advisors’ ability to deliver sound and evidence-based IPM recommendations to both onion sets and food onion producers for the control of Fusarium basal rot and onion fly. By focusing on these knowledge gaps, the QualityOnion will develop new Fusarium detection and quantification methods, study how to combat the different Fusarium species infecting onions in Norway, develop a monitoring system and forecasting model for onion fly and study whether infestation by arthropod pests can predispose onion to Fusarium and vice versa. The QualityOnion will substantially improve our knowledge and understanding of Fusarium basal rot and onion fly. We hypothesize that improved knowledge of diagnostics, monitoring, forecasting, as well as interactions between fungal and arthropod pests, will improve the IPM strategies, and thus, help onion producers to reduce the yield losses related to onion fly and Fusarium basal rot. In addition, the QualityOnion contributes to reduced production costs and anti-resistance strategies by guiding the use of pesticides only where and when necessary. Altogether, the QualityOnion helps to extend the time that Norwegian onions are available on the market. By promoting profitability, food safety, and food security, the QualityOnion project will make a major contribution to sustainable onion production in Norway.