Flea beetle

What you see

Tiny 2-3 mm shiny black or striped beetles that spring away like fleas when your shadow falls on them.

Damage

Leaves peppered with dozens of small round shot-holes. Seedlings can be riddled and checked; older plants usually survive but look chewed.

Lifecycle on this coast

One or two generations. Adults overwinter in debris and hedgerows and emerge in warm dry spring weather. They are far worse in hot dry spells.

When to act

Cosmetic on mature plants - tolerate freely. Act only on seedlings, where shot-holing can kill.

Months: April, May, June, July, August

Plants it bothers

Rocket, Radish, Turnip, Mustard greens, Mizuna, Cabbage, Wild rocket, Komatsuna

Natural enemies

Ground beetle, Rove beetle, Parasitic wasp

Remedies

Insect mesh and fleece barrier, Diatomaceous earth, Encourage predators

The thing people get wrong

Flea beetles hate humidity and hate being wet. Keeping the seedling bed damp, and covering it with fleece for the first three weeks only, gets a rocket or radish crop past the vulnerable stage - after which the shot-holes are ugly but harmless, and the plant outgrows them completely.