The cabbage root fly lays its eggs in the soil beside cabbage plants. The larvae feed on the roots, with the result that the plant wilts and dies. On pulling up the part underground, it will be found to consist of just the main taproot with all the small feeder roots missing. Protection is provided by making a felt disc 10cm/4in in diameter with a single cut from the circumference to the centre to allow it to be placed around the stem.