Swede Midge (Contarinia nasturtii Keiffer) Phenology and Management in Minnesota Community Gardens

Swede midge is a major insect pest of brassicas, including broccoli (Brassica oleracea L. var. italica), cauliflower (B. oleracea L. var. botrytis), collards (B. oleracea L. var. viridis), and kale (B. oleracea var. sabellica). The insect infests and feeds on the growing tips of plants, resulting in distorted leaves or lack of heading of broccoli and cauliflower. Since 2014, when continuous trapping began in Minnesota, USA, it has primarily been found in community gardens in the Twin Cities metropolitan area. Trapping data obtained at Saint Paul community gardens over 3 years indicated that swede midge phenology in any particular garden varied from year to year. Gardeners surveyed in 2023 indicated some knowledge of swede midge, were unsure of how to recognize infestation symptoms, and were interested in collaborating to test management methods. A simple mitigation system using bamboo poles, polypropylene fabric, and weed barrier was tested for its ability to reduce infestations by blocking access to plants by adults and to soil by larvae and prevent emergence by previously pupating generations. It was 50% to 80% effective compared with unprotected controls.