Asparagus beetle

What is asparagus beetle?

Asparagus beetle is a pest both in its adult and larval stages. They eat the foliage, and also gnaw bark from the stems, causing growth above the point of damage to dry up.

Symptoms

• The adult beetles are 6-8mm long (about 1/4in), black in colour with six yellow blotches on their wing cases and a reddish thorax
• Both the adult beetles and their grubs feed on asparagus foliage and bark
• If the bark around the stem circumference has been completely removed, the stem and foliage above dries out and turns yellow brown

Control

Non-chemical control

Burn old stems at the end of the year to destroy overwintering beetles. Hand pick the beetles and larvae from plants when seen from late spring onwards.

Chemical control

Large plantings, where hand removal is not feasible, can be sprayed with pyrethrum (Py Spray Garden Insect Killer, Doff All in One Bug Spray or Scotts Bug Clear Gun for Fruit & Veg). If the plants are in flower, spray at dusk to avoid harming bees.

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

• The beetles emerge from the soil in May and June and lay elongate black eggs that are attached by one end to the asparagus spears and foliage
• The creamy greyish-black larvae are up to10mm long (3/8in) when fully grown, after which they go into the soil to pupate
• There are two generations between May and September
• In the autumn, adult beetles seek sheltered places where they overwinter