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.