Flea beetle
Tiny dark beetles that jump when disturbed and pit young brassica leaves with small round holes, giving a shot-holed appearance. Seedlings can be checked badly; established plants shrug it off, so the timing of the attack decides whether it matters at all.
Caused by: Phyllotreta spp. · also called turnip flea beetle
Described view
A broccoli leaf showing both patterns together: large ragged areas eaten away to the midrib with green-and-yellow cabbage white caterpillars and dark frass pellets still present, and a separate area of the same leaf peppered with the tiny round shot-holes of flea beetle
What brings it on
Warm dry weather in spring and early summer, on young brassicas. Damage is far worse on a checked or slow-growing seedling than on one growing away strongly.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Flea beetle
Checked 2026-08-13
Usually seen: April, May, June, July, August
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Cover young brassicas with insect-proof mesh from sowing. Keeping seedlings watered and growing quickly is the other half — a plant that grows through the attack escapes it.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Flea beetle — prevention
Checked 2026-08-13
Dealing with it once it is there
- Water and feed to push growth on. There is little worth doing to the beetles themselves on a garden scale, and an established plant outgrows the damage.
source
Sourced guidancemoderate confidence
- Royal Horticultural Society: Flea beetle — control
Checked 2026-08-13
What it affects
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.
Plant-specific guides
Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.