What are holm oak leaf-mining moths?

Leaf-mining moths are small insects with caterpillars that feed inside leaves, creating discoloured blotches and meandering lines where the internal tissues have been eaten away.

Symptoms

Look out for typical symptoms;

• Holm oak blotch leaf-miner (Phyllonorycter messaniella) causes pale brown, elongate oval discoloured areas on the upper leaf surface where caterpillars have eaten out the internal leaf tissues. The underside of these mines is whitish brown. 
• Holm oak linear leaf-miner (Ectoedemia heringiella), causes brown linear mines that end in a blotch. This is mainly in south-eastern England, where it was first discovered in 2002, but is becoming more widespread. It may now be the more common of the two species of holm oak leaf mining moth
• The presence of the mines is usually most obvious in spring, until the old leaves drop in early summer

Control

Holm oaks tolerate the damage and continue to grow, even when most leaves are affected. The appearance of  will improve in early summer, when new foliage develops and some of the old mined leaves are shed. Leaf miners can be part of a healthy balanced garden. 

There is no control available for holm oak leaf-miners, although there are several predators and parasites that can limit populations. In some areas birds such as blue tits have learnt to open the mines to feed on the caterpillar within. 

Biology

The leaf-mining moth, Phyllonorycter messaniella has three generations a year. Larvae feed within the leaves during July, October, and from November to March. When fully fed, the larvae pupate within the leaf mines. By late winter, much of the foliage on a holm oak may be affected. The adult moth has brownish-white wings with a span of almost 8mm.

Mines caused by Ectoedemia heringella develop during spring and are fully formed by the end of May. The adult moth has a wingspan of 5-6 mm and the forewings are white and black in colour.