Flea beetle can be a problem in the vegetable garden during May and June & the signs are there to see if you know what to look for. They attack members of the brassica family including radish. This photo shows the typical ’shot hole’ damage made by a flea beetle on a radish leaf.
The young leaves can end up looking a bit tattered.
Seedlings may be wiped out by an attack of flea beetle, but usually the plants grow away from the problem if growing conditions are good. Seedlings are most vulnerable to flea-beetle when stressed, particularly by dry, poor seedbeds where crop growth is slow.
Flea beetles are tiny, usually shiny and black, and jump away when disturbed. The following picture shows a black dot on the top left of the cotyledon, which is a flea beetle & indicates how tiny flea beetles are:
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.
Bob Flowerdew method – coat on side of a card with treacle & wave the card over the effected plants. The flea beetle will stick to the treacle as it jumps off the leaves!
Cover the row immediately after sowing – with ultra-fine mesh netting (0.8mm mesh) or horticultural fleece. This will keep the flea beetle out.
It is worth taking a few simple control measures when the first sign of flea beetle is seen.