The Asparagus Beetle

Crioceris asparagiis the common asparagus beetle. From legs to antenae this insect grows to be about 1/2-inch long. It has a black and orange shell on its back with six irregular (but nearly square) white spots arranged in two rows vertically. A close cousin, Crioceris duodecimpunctata has an orange shell with twelve randomly-placed small black dots. Both will feed on asparagus, but the common beetle will do far more damage.

Sketch of Common Asparagus Beetle

Common asparagus beetles will live throughout the winter in the hollow stalks of old asparagus plants. For this reason, it is wise to clear old asparagus stems and foliage away and destroy them in the late fall. They may also be found under leaves on the ground. In the early spring the females lay their eggs on asparagus spears that are just breaking the surface. Within a week, the eggs will hatch and larvae crawl out to devour new asparagus spears and foliage. The spear heads may bend over into what is often refered to as a "shepherd's crook".

After about two weeks the larvae fall to the ground where they pupate, or turn into the adult stage. They then will climb back up the asparagus plants and feast on the fern-like foliage. They can be fairly thorough, in which case they will weaken the plant to a degree that it may not be able to accumulate enough stored energy and nutrients to push up spears the next year.

The orange, twelve-spotted beetle arives later and tends to eat the fruit of the plant rather than the leaves.

There are several methods to control the asparagus beetles. The mode of control depends on the level of infestation and the size of the patch or field.

  • The most basic method is hand-picking the beetles and depositing them in a bucket of soapy water. This requires diligent inspection of the garden, as beetles can fly in at any time.
  • Getting rid of dried old stalks of most garden plants especially in the late fall is wise. They can harbor various beetles and other pests. Keep the garden neat and clean.
  • A small parasitic wasp, the Tetrastichus asparagi, likes to lay its own eggs inside of the eggs of the asparagus beetle. They can destroy up to 70% of the beetle eggs.
  • Lady beetle larvae will eat the eggs of the asparagus beetle.
  • The beetle can be controlled using an insecticide such as pyrethrins or malathion. When using insecticides read and follow all label instructions carefully.

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