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Leafhoppers: how to recognise and treat it

Pest

Leafhoppers — Photo: Josve05a /Wikimedia Commons (CC BY 2.0), CC BY 2.0, Wikimedia Commons

Symptoms

Fine pale specks (stippling) or coarse pale mottling on the upper leaf surface.
Spots can merge so leaves look yellowed, like a nutrient deficiency; damaged leaves stay discoloured.
On potatoes and beans, "hopperburn" — leaf tips and margins curl, turn yellow to brown and become brittle, as if scorched.
Small wedge-shaped insects that jump or fly when disturbed; pale wingless nymphs and their white cast skins on the leaf undersides.

Organic treatment

Usually no control is needed — leafhoppers rarely affect plant growth; herbs with mottled leaves are safe to eat.
If nymphs are abundant early in the season, thoroughly spray shoots and leaf undersides with insecticidal soap, horticultural oil or neem oil; repeat for large populations.
Encourage natural enemies — birds, ladybirds, lacewings, spiders, ground beetles and parasitic wasps.

Chemical treatment

For large numbers on vegetables, pyrethrum (pyrethrins) sprayed early in the day on the leaf undersides; follow the label dose and pre-harvest interval. Sprays do not prevent diseases that leafhoppers spread, because the insects pass them on before they die.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

From late winter, check leaf undersides and green shoots for nymphs if leafhoppers were a problem last year.
Cover vegetables with row cover as soon as seedlings emerge or are planted out, taking care not to trap leafhoppers underneath.
Keep weeds down, especially perennial weeds that shelter leafhopper eggs.

Sources

Figures checked against these sources.