asparagus beetle

Symptoms

Adult beetles (6-8mm, blue-black with red + yellow markings) feeding on spears + fern, slug-like grey-green larvae (up to 8mm) on fern stems, dark brown eggs in rows on spears + fern, severe defoliation in summer weakens crowns, gnawing damage on emerging spears makes them unmarketable.

Easily confused with

• asparagus rust

  How to tell them apart: Both leave asparagus fern yellowing and browning in summer, but look closely at the foliage surface. Asparagus beetle (Crioceris asparagi) shows the cause physically present: 6-8 mm blue-black beetles with creamy-yellow squares and red margins, slug-like grey-green larvae on the stems, rows of dark upright eggs glued to spears and fronds, and chewed, stripped, ragged cladophylls. Asparagus rust (Puccinia asparagi) leaves the foliage intact but blistered: raised powdery pustules that rub off as orange-rust dust in summer, turning to brick-red then black crusty streaks along the stems in autumn, with no insects and no chewing. If you see beetles, larvae or egg rows it is the beetle; if you see powdery orange-to-black pustules on otherwise uneaten stems it is rust.