Colorado beetle

What you see

Unmistakable: rounded 10 mm beetle with ten black stripes down a yellow back. Larvae are fat, brick-red, humped grubs with rows of black dots along each side.

Damage

Rapid, total defoliation of potato haulms - a row can be stripped to stems within days. Clusters of orange eggs on leaf undersides.

Lifecycle on this coast

One to three generations. Adults overwinter deep in the soil and walk to the new crop in spring, which is why rotation to a distant bed genuinely helps.

When to act

Very low tolerance - they defoliate faster than the plant can recover. Hand-pick from the very first beetle.

Months: May, June, July, August

Plants it bothers

Potato, Aubergine, Tomato

Natural enemies

Ground beetle, Bird, Parasitic wasp

Remedies

Encourage predators, Bacillus thuringiensis (Bt)

The thing people get wrong

On a garden scale hand-picking genuinely beats everything, provided you also crush the orange egg clusters underneath the leaves. Adults, larvae and eggs into a jar of soapy water, every second day for two weeks, ends the problem for the season - and a bed rotated far from last year's potatoes gets colonised far more slowly.