Scientific name Phyllonorycter leucographella
Plants affected Mainly Pyracantha (firethorn)
Main cause Caterpillars of the moth feed inside the leaves, causing distinctive oval-shaped mines
Timing Mainly January-March
What is pyracantha leaf-mining moth?
This moth was discovered new to Britain in Essex in 1989 but has now spread throughout England and into Scotland. The wings of this small moth (6-8mm wingspan) are bronze, with white markings. The moth's caterpillars feed inside the foliage of Pyracantha, where they cause a distinctive silvery white discoloration on the upper leaf surface. Images of the adult can be found at UK moths (external link)
The leaf mines cause by this moth can be seen on Pyracantha during the summer but they are much more frequent during the early months of the year. The caterpillar initially feeds by making a linear mine along the central leaf vein. Later the mine broadens until there is an oval silvery white area that occupies most or all of the upper leaf surface. When the caterpillar has completed its feeding, it causes the leaf to fold upwards, and the mine becomes less visible.
In some years, a high proportion of the leaves will have mines in them during January-March. This can give the plant an unhealthy appearance but this moth has little impact on the plant's growth, its ability to produce flowers and berries, or its long-term health. The old mined leaves may drop off in spring but new growth will restore the plant's appearance.
Although leaf mining damage may be considered unsightly, it is unlikely to affect the health or vigour of an established tree or shrub and it does not need to be controlled. Leaf miners can be part of a healthy balanced garden, most species will have natural enemies including parasitoid wasps. Birds such as blue tits can sometimes open mines to consume the larvae within.
The moth lays eggs on the foliage and after hatching the larvae bore into the leaves where they feed on the internal tissues. This moth has up to three generations per year and is active throughout much of the year, it is the late winter generation that is the more abundant and noticeable on pyracantha. When the caterpillar has completed its feeding it spins silk webbing within the mine. The mine contracts, causing the leaf to fold upwards, with the insect pupating within the folded leaf. Although Pyracantha is the principal host plant for this moth, it can also develop during the summer in the foliage of apple, hawthorn, mountain ash and whitebeam. I
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