Integrated Pest Management Strategies with Fine-Mesh Row Covers Increase Yield and Quality of Organic Bok Choy and Napa Cabbage

Feeding damage from flea beetle and harlequin bug reduces the marketability of brassica crops, including bok choy and napa cabbage. Fine-mesh row covers can be used as a pest management strategy to augment, reduce, or replace organic-compliant insecticides. However, different mesh sizes may vary in their potential to protect against small-bodied pests like flea beetles. Across four experiments in the spring and fall of 2024 and 2025, we compared the effects of two fine-mesh row covers, with and without organic insecticides; a rotation of the organic insecticides spinosad and pyrethrins; and an uncovered control on pest insect abundance, flea beetle feeding damage, and yield in organic spring bok choy and fall napa cabbage production. In the first experimental season (Spring 2024), we tested ExcludeNet row cover (mesh size: 0.95 3 0.95-mm); after observing that flea beetles could infiltrate the mesh, we incorporated a second row cover product (ProtekNet; mesh size: 0.35 3 0.35-mm) in subsequent experiments. Compared with the control, ProtekNet always (in three of three experiments) significantly reduced flea beetle abundance as measured through weekly visual surveys, while a significant reduction was observed in three of five ExcludeNet treatment–experiment combinations. Row covers always reduced flea beetle feeding damage compared with the control. When harlequin bug was present, in the fall napa cabbage experiments, row covers proved more effective than the organic insecticide treatment for its management. Marketable yield was significantly higher in all ProtekNet and three of five ExcludeNet treatment–experiment combinations relative to the corresponding control. Fancy-grade marketable yield was significantly higher in row cover treatments than the control and significantly higher in ProtekNet treatments than the organic insecticide treatment. This study demonstrates that row covers hold promise as a pest management strategy, but depending upon the mesh size, integration with organic insecticides may be necessary forsomepestgroups,includingflea beetles and caterpillars. Limitations with the relatively large mesh size of ExcludeNet and low durability of ProtekNet reveal the need for future studies to identify optimal row cover mesh size and material durability for flea beetle management in organic brassica crop production.