Organic farming with its reliance on natural fertilizers, cover cropping, and crop rotation, presents a sustainable approach to food production. However, a significant challenge in organic production is insect and disease management. Organic insecticides often have limited efficacy, are expensive, and require repeated applications. Mesotunnels, medium-sized (36-40 inches tall) tunnels covered with insect netting, have emerged as a pest management tool for organic vegetable growers. This study evaluated the effectiveness of mesotunnel and low tunnel systems for pest management and season extension in organic Chinese cabbage (cultivar ‘Minuet’) production. The first season of this two-year study was conducted in Fall 2024 on certified organic land at Iowa State University Horticulture Research Station, Ames, IA. The experiment was set up as a randomized complete block design with four replications and following treatments: i) 85 g ExcludeNet insect netting, ii) 0.55 oz Agribon row cover, iii) 85 g ExcludeNet insect netting + OMRI-listed insecticide iv) OMRI-listed insecticide, and v) an untreated control, uncovered with no insecticide. Weekly pest surveillance focused on Brassica insect pests such as aphids, loopers, harlequin bugs, flea beetles, and their damage was recorded. Hobo data loggers recorded variations in light intensity, air and soil temperature, and relative humidity to observe microclimate variations in each treatment. At harvest, yield data was categorized as marketable or nonmarketable and graded according to USDA commercial standards. Among all treatments, the highest marketable produce was recorded in ExcludeNet + OMRI-listed insecticide treatment (42%), followed by Agribon row cover (31%) and the lowest in OMRI-listed insecticide (15%) during the first harvest. The earlier maturity in these treatments was likely due to warmer temperatures and improved humidity regulation under the tunnels. The insect abundance and their damage on leaves was significantly lower in ExcludeNet & ExcludeNet + OMRI-listed insecticide treatment. Integrating netting and row covers with limited use of organic insecticides provided the highest pest suppression, suggesting that physical barriers can effectively optimize pest management and enhance marketability in organic vegetable production systems. Findings from this study will inform growers and the research community about the feasibility of insect nettings as a sustainable pest management tool in organic specialty crop systems.
