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Colorado Potato Beetle: how to recognise and treat it

Pest

Colorado Potato Beetle — Photo: Adámozphoto, CC BY-SA 4.0, Wikimedia Commons

Symptoms

Oval yellowish beetles about 1 cm long with ten black stripes on their wing covers.
Humpbacked dark-red larvae with two rows of black spots on each side, often feeding in groups.
Clusters of yellow-orange eggs on the undersides of leaves.
Leaves eaten down to the stems; heavy attacks can strip potato plants completely.

Organic treatment

Hand-pick adults and larvae into a pail of soapy water and crush the egg clusters on the undersides of leaves.
Remove the overwintered beetles that appear on young plants in spring before they lay eggs.
Spray Bacillus thuringiensis var. tenebrionis, neem (azadirachtin) or spinosad when the eggs start to hatch; they work only on very young larvae.

Chemical treatment

A pyrethroid insecticide labelled for potatoes (for example lambda-cyhalothrin, where approved) or spinosad, sprayed while the larvae are small; beetles quickly become resistant, so do not spray more than one or two times per generation, and follow the label dose and pre-harvest interval.

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

Prevention

Grow potatoes and other nightshades as far as possible from last year's plot; adults overwinter in the soil and usually walk to the nearest crop.
Use row covers over young plants, but only where no nightshade crops grew the previous season, as beetles may emerge from the soil under the cover.
Dig over the soil after harvest to reduce the beetles overwintering in it.

Plants it affects

Sources

Figures checked against these sources.