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Asparagus beetles

Quick facts about asparagus beetles

The common asparagus beetle and the spotted asparagus beetle feed on asparagus spears and cause browning and scarring.

  • Start looking for these pests in early May or just after asparagus plants emerge and continue for the rest of the growing season.
  • The best time to check for asparagus beetles is in the afternoon when they are most active.
  • You can control common asparagus beetle adults and larvae by handpicking them and dropping them in a pail of soapy water.
  • If you find a lot of asparagus beetles in your garden you may want to use a pesticide.

How to identify asparagus beetles

It is important to correctly identify the two different kinds of asparagus beetles because the common asparagus beetle is found more often and causes more damage.

Both types of asparagus beetle adults are ¼-inch long with oval-shaped bodies and moderate length antennae.

  • The adult common asparagus beetle (Crioceris asparagi) is bluish-black with six cream colored spots on its back.
  • Adult spotted asparagus beetles (Crioceris duodecimpunctata) are reddish-orange with twelve black spots.
Common asparagus beetle with 6 cream-colored spots crawling on stem
Common asparagus beetle
Spotted asparagus beetle crawling on asparagus fern
Spotted asparagus beetle

The larvae of both species are slug-like with visible heads and legs.

Two asparagus beetle larvae on a stem, each with head and legs visible
Common asparagus beetle larvae
  • Common asparagus beetle larvae are light gray with a black head.
  • Spotted asparagus beetle larvae are orange.

Spotted asparagus beetles should not be confused with beneficial lady beetles.

Lady beetle adults have oval to rounded, dome-shaped bodies with a varying number of spots. They also have heads that are partly to completely hidden when viewed from above, and short antennae.

Life cycle of asparagus beetles

Common asparagus beetle adults can live through the winter in sheltered places such as under loose tree bark or in the hollow stems of old asparagus plants. Adults appear in gardens just as the asparagus spears are coming out of the soil in spring.

Common asparagus beetles lay dark brown, oval-shaped eggs in a row
Common asparagus beetle eggs

The beetles lay many dark brown, oval-shaped eggs in rows on the spears, ferns or flower buds of asparagus plants.

  • The eggs hatch within a week.
  • The larvae move to the ferns to start feeding.
  • They feed for about two weeks and then fall to the ground to transform into pupae in the soil.
  • About a week later, adults emerge to start another generation, feeding on the ferns for the rest of the growing season.

The spotted asparagus beetle has a similar life cycle but usually appears in gardens later than the common asparagus beetle in mid-May. It is gone by late July.

They lay greenish eggs on the ferns. The orange larvae feed on the berries of the asparagus.

Damage caused by asparagus beetles

Bent over asparagus spear due to damage from asparagus beetle feeding

Asparagus spears become brown and bend over into a hook when either species of asparagus beetle adults feed on the spears.

Once the ferns appear after the harvest of asparagus, the common asparagus beetle larvae and adults can also feed on the ferns.

Beetles feeding on the leaves weaken the plant and reduce the plant's ability to provide sufficient nutrients for the following season. Fewer leaves also make asparagus a target for Fusarium, a fungal disease.

The spotted asparagus beetle larvae feed on asparagus berries and do not affect the health of the plant. The presence of common asparagus beetle eggs on the spears can make the asparagus unappealing.

How to protect your garden from asparagus beetles

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Jeffrey Hahn, Extension entomologist and Suzanne Wold-Burkness, College of Food, Agriculture and Natural Resource Sciences

Reviewed in 2018

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