The brightly coloured, metallic-green beetles have steel-blue spots on their scutellum and elytra and are about 8 mm in length. Their bodies are compact, streamlined and similar to those of click beetles. However, unlike click beetles, cypress jewel beetles are not able to turn by “clicking” once they fall on their backs.
The females use their ovipositors (egg laying organ) to make a short incision into the bark of the tree and deposit their eggs in the phloem between the bark and xylem. The larvae hatching from these eggs have no legs, are cream-coloured and have strongly sclerotic mandibles at the front. Their tunnels are found in the phloem and on the surface of the xylem of younger twigs.
These tunnels have a flat, oval profile (like the larvae). Once these tunnels encircle the branch they cut off the sap flow and the branch withers. The larvae pupates into a small, vertical hole in the wood in spring after the wintering period.
An adult jewel beetle emerges from the pupa in early summer, around the time when lime trees begin to flower, closing the cycle.
Only one generation of beetles develops per year.
Cypress jewel beetles cause characteristic damage through the tunnels and galleries produced by their larvae: individual branches wither and turn brown in otherwise healthy appearing thujas. The primary cause of the damage becomes visible, when cutting into the surface of the bark of such branches: wide, flat tunnels that are partly filled with feed and excretion particles can be found between the bark and xylum. These galleries cut off the sap flow to the branches causing their scaly leaves to wither and turn brown. Typically, only individual branches will turn brown, not the entire plant.
Cypress jewel beetles live on various plants in cypress family, such as juniper, thujas, false cypresses,…. .
- Cut off parts (branches, twigs) that are heavily infested.
- Chemical treatment is not considered useful at present.
- Decisions whether to take action or not should be based on the individual case; after all, this is a beautiful and rare beetle.