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Flea beetles

Flea beetles are tiny shiny beetles that pepper the leaves of seedlings with small holes. Established plants shrug them off, but a bad attack in a dry spring can kill young brassicas, radishes and rocket.

Pests
Radish seedlings peppered with tiny flea beetle holes
Radish seedlings peppered with tiny flea beetle holes

What it looks like

The holes look like buckshot.

  • Dozens of round holes 1 to 3 mm across.
    Shot-holes Dozens of round holes 1 to 3 mm across.
  • Shiny black or striped beetles hop away when touched.
    Jumping beetles Shiny black or striped beetles hop away when touched.
  • Some holes do not go right through, leaving pale pits.
    Pitted leaves Some holes do not go right through, leaving pale pits.
  • Heavily holed seedlings stall and wilt.
    Stunted seedlings Heavily holed seedlings stall and wilt.

How to confirm it

Watch the plant on a warm day.

  1. Hover a hand

    Beetles jump like fleas as your hand approaches.

  2. Check the size of holes

    Small and round, not ragged.

  3. Dry weather

    Worst in warm, dry spells in spring.

What to do

Protect seedlings until they grow away.

  1. Cover with fleece or mesh

    Fine mesh from sowing keeps them off.

  2. Water often

    Keep seedlings moist and growing fast; beetles dislike damp.

  3. Sticky trap

    Pass a sticky card low over plants to catch jumping beetles.

  4. Sow later

    Sow a little later in spring, when growth outpaces damage.

Prevent it next time

  • Keep the bed weed-free, especially of brassica weeds.
  • Cover early sowings.
  • Clear plant debris in autumn.

What not to do

Do not panic at holes on mature leaves; the plant is past the risky stage.

In the growing guides

Where the guides mention it, with plant-specific advice.

Sources

  1. Flea beetles on brassicas and allied plants, Royal Horticultural Society
  2. Flea beetles on vegetables, University of Maryland Extension