Flea beetles (subfamily Alticinae) are small, shiny beetles — typically 2–3 mm long — that jump like fleas when disturbed. Several species are significant pests of vegetable crops, particularly brassicas, radishes, and rocket. They create characteristic “shothole” damage that can weaken or kill young seedlings.
What Damage Do Flea Beetles Cause?
Adult flea beetles chew small, round holes in leaves, creating a distinctive shothole pattern — dozens of tiny perforations that make leaves look like they have been peppered with fine shot. While established plants can usually tolerate this damage, seedlings are vulnerable. Heavy infestations can kill young plants before they become established.
Signs of Flea Beetle Damage
- Shothole leaves: Dozens of tiny round holes (1–2 mm) in leaves
- Wilting seedlings: Young plants weakened by excessive leaf damage
- Pitting on stems: Surface grazing on stems of young plants
- Jumping beetles: Tiny shiny beetles that leap away when disturbed
- Worst period: Late April to June when adults emerge and seedlings are small
Which Plants Are Affected?
| Flea Beetle Species | Target Plants | Appearance |
|---|---|---|
| Cabbage stem flea beetle | Brassicas (cabbage, kale, broccoli, turnip) | Metallic blue-black, 3–4 mm |
| Large striped flea beetle | Brassicas, radish, rocket | Yellow stripes on black, 3 mm |
| Small striped flea beetle | Brassicas, mustard | Yellow stripes on black, 2 mm |
| Potato flea beetle | Potatoes, tomatoes, aubergines | Dark brown-black, 2–3 mm |
How to Protect Plants from Flea Beetles
- Use fleece or mesh. Cover seedlings with horticultural fleece or fine mesh (Enviromesh) immediately after sowing. This is the most effective organic method.
- Sow later. Delay sowing brassicas until late May or June when seedlings grow faster and flea beetle pressure begins to ease.
- Keep soil moist. Flea beetles thrive in hot, dry conditions. Regular watering around seedlings creates less favourable conditions.
- Grow seedlings under cover. Start brassicas in modules and transplant as larger, more resilient plants.
- Use sticky traps. Yellow sticky traps placed near plants can catch adult beetles.
Did you know? Flea beetles can jump up to 50 times their body length — equivalent to a human jumping the length of a football pitch. This remarkable ability is powered by a spring-loaded mechanism in their enlarged hind femora.
Key Takeaway
Flea beetles can be harmful to young plants, especially brassica seedlings. The most effective defence is physical exclusion with fleece or fine mesh. Established plants can usually tolerate the damage without significant yield loss.