Flea beetle can be a problem in the vegetable garden during May and June. They attack members of the brassica family including radish.

Various genera and species of flea beetles cause problems in the garden, all members of the Chrysomelidae family. One example is the cabbage stem flea beetle (Psylliodes chrysocephala).

Plants affected

Cruciferous plants such as cabbage, cauliflower, brussel sprouts, kale, turnip, swede, radish, salad rocket. Other plants, such as nasturtium and stocks can also be attacked.

Symptoms

Small, rounded, irregular holes in cotyledons and leaves of seedlings. In severe cases the leaves look as if they had been peppered with fine shot.Seedlings are most vulnerable to flea-beetle when stressed, particularly by dry, poor seedbeds where crop growth is slow.

Flea beetle life cycle

Flea beetles overwinter in leaf litter as adult beetles & emerge in spring to attack the seedlings of brassicas and other host plants. They are quite mobile and may fly a kilometre to find food. In late summer there is sometimes a significant migration of adult beetles from oilseed rape fields into gardens when damage to mature plants can occur.Female beetles lay their eggs in the soil near suitable plants in May/June. The larvae of the large striped flea beetle feed in ‘mines’ in leaves; the larvae of other species feed on plant roots, but this does not usually cause severe damage. These larvae pupate in the soil, new adults hatching out in the autumn. Adults feed for a few weeks before hibernating. These adults will survive until the following July or August.

Control of Flea Beetle

• Provide ideal growing conditions: Prepare the soil well and choose appropriate sowing times to encourage rapid and vigorous growth of young plants, so that they grow away from the flea beetle. Keep the seed bed moist as damage is always worse in hot dry weather.
• Grow a trap crop: A sacrificial row or two of radishes, which seem to be the flea beetle’s favourite, may help to protect other young brassicas from attack by diverting the beetle’s attention.
• Cover the crop: Horticultural fleece or Enviromesh will keep flea beetles off if put in place immediately after sowing.
• Tidy up: Clear the garden of all rubbish to reduce the number of overwintering sites. Weed control in and around the seedbed deprives larvae of food sources.
• Use sticky traps - white and yellow sticky traps placed every 15 to 30 feet of row will catch the beetles. Encircling the plot with continuous sticky tape is also used.
• Chemical control - chemicals are sold in garden centers for flea beetle control. Always read the label.
• Biological control - Microcotonus vittage Muesebeck, a native braconid wasp, kills the adult flea beetle and sterilizes the female flea beetle.