Leaf miners overwinter in soil as grubs and emerge as flies during the growing season. There are multi-generations every year. To control them, try the following:
- Plant beets and Swiss chard in a new location, practising smart crop rotation.
- Cover your plants with a crop cover (a lightweight white polyester fabric) to prevent egg-laying by adult flies. This material should be available at your local garden centre or nursery. The fabric allows air and moisture to the plants. Be sure to leave enough slack in the material, but anchor it securely and bury the edges in the ground.