Very small shiny black beetles sometimes with a yellow stripe running along each wing case. They eat small, circular holes on the upper leaf surface which often do not go all the way through the leaf. Heavy attacks can kill seedlings. Flea Beetles affect a range of plants including brassicas - swede, turnip, radish,aubretia, wallflowers, stocks and alyssum.
Cultural measures: Remove all plant debris. Thoroughly prepare soil before planting. Protect seedlings through the vulnerable seedling stage by sowing when weather conditions allow rapid germination and establishment. Water young plants in dry weather. Protect seedlings with horticultural fleece until established.
There is no product registered to control flea beetles on swede.