WHAT IS IT?
The flea beetle species Phyllotreta and Psylliodes cause damage to brassica plants and related plants, including radish, turnip, mustard, rocket and nasturtium. The beetles are black (or can be blue-green or even striped). They are about 2-3mm (1⁄10in) in length and have long hind legs, which enables them to leap into the air when disturbed. They hibernate in numbers over the winter and emerge in spring, but affect summer plants too.