Asparagus Beetle: how to recognise and treat it

Pest

Symptoms

Beetles 6–8 mm long, blue-black with six cream-yellow blotches on the wing cases and a reddish thorax; the related spotted asparagus beetle (Crioceris duodecimpunctata) is reddish orange with twelve black spots.
Small dark, elongate eggs standing on end on the spears and foliage.
Grey, slug-like larvae with a black head, up to 1 cm long, feeding on the ferny foliage.
Spears chewed, scarred and bent; foliage stripped and stems gnawed, so the growth above turns yellow-brown and dries up.

Hand-pick beetles and larvae and rub off the eggs from spring onwards; shake infested stems over a container to collect the larvae.
Use the biological control with the nematode Steinernema carpocapsae against the larvae.
Against the spotted asparagus beetle, gather and destroy the berries, where its larvae feed.

Only if beetles or larvae are numerous — spinosad, pyrethrins, neem or a pyrethroid labelled for asparagus; spray late in the day to spare bees 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.

Harvest all the spears every day during the season, so eggs and larvae have less time to develop on them.
Clear away old stems, weeds and plant debris in autumn, where adult beetles overwinter.
Grow all-male varieties, which set no berries and so give the spotted asparagus beetle nowhere to breed.
Encourage birds, frogs, ground beetles and ladybirds, which eat the larvae; small numbers of beetles can be tolerated.

Figures checked against these sources.