Asparagus beetle

What you see

Striking 6 mm beetle, metallic blue-black with cream squares and a red border. Larvae are dull grey humpbacked grubs that cling to the ferns.

Damage

Bare patches chewed on spears and stems, browning and defoliation of the summer ferns. Rows of small dark eggs standing on end along the spears.

Lifecycle on this coast

Two or three generations. Adults overwinter in old fern debris and hollow stems - so autumn clearance is the main control.

When to act

Tolerate a few on established beds. Act if the summer ferns are being stripped, since that is where next year's crown energy comes from.

Months: April, May, June, July, August

Plants it bothers

Asparagus

Natural enemies

Parasitic wasp, Ladybird, Bird

Remedies

Encourage predators, Insecticidal soap spray

The thing people get wrong

Protecting the summer FERNS matters more than protecting the spears you eat. Those ferns are recharging the crown for next spring, and a bed defoliated in July gives thin spears next April - so the beetle you shrug off in summer is the one that costs you the harvest.