Hellebore leaf miner

What is hellebore leaf miner?

Hellebore leaf miner is a small fly with larvae that tunnel inside the leaves of Helleborus foetidus.

Symptoms

• Only Helleborus foetidus is affected by this pest.
• The mines in the leaves are initially brownish-black blotches, but later become sinuous, whitish-brown tunnels.
• In heavy attacks, most of the foliage will be disfigured by spring.
• Damage develops during late summer to early spring.

Control

Non-chemical control

• Although the mines can be unsightly, H. foetidus plants are not greatly harmed and so the damage can be tolerated.
• Heavily mined leaves can be cut off and destroyed during the winter before the adult flies emerge.

Chemical control

• The systemic insecticides Provado Ulimate Bug Killer (thiacloprid) and Bug Clear Ultra (acetamiprid) may give control of newly hatched hellebore leaf miner larvae if applied in August.

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Biology

• This small fly was first discovered in Britain in 1999 but is now widespread in England.
• Eggs are laid on the foliage and the larvae begin feeding inside the leaves during August.
• The mines are not fully developed until the new year. Pupation takes place within the leaf mines.