Holly leaf miner

What is holly leaf miner?

Holly leaf miner is a small fly with larvae that cause discoloured blotches by feeding inside holly leaves.

Symptoms

• Yellowish-white or yellowish-purple blotches occur on the upper surface of the older leaves, usually near the centre of the leaf.
• Leaves with mines may turn yellow and drop in early summer, but this is the natural shedding of older leaves, and not due to the pest.

Control

Non-chemical control

• Although the mines may be considered unsightly, this pest can be tolerated as it has little real impact on the health and vigour of a holly.
• On small specimen plants it is feasible to remove mined leaves, but not if this would result in significant defoliation.
  

Chemical control

• Insecticides are unlikely to be effective as the thick, glossy surface of holly leaves means that sprays run off the foliage and do not penetrate to where the grubs are feeding.

Biology

• Grubs of the holly leaf miner tunnel inside the leaves.
• There is one generation a year, and the adult flies lay eggs on the new foliage in May to June.
• When the larvae have completed their feeding in the following spring, they pupate inside the leaf mines