The shape of the leaf mine caused by the caterpillars of laburnum leaf mining moth is a circular blotch which, when fully developed, can be seen on the upper leaf surface as a brown area about 10-15mm in diameter. It is the only leaf mining moth likely to affect Laburnum in Britain.

There are usually two generations of the moth during the summer, with caterpillars feeding in late June-July and in September. In hot summers there may be a third generation. In some cases leaves can contain several mines which coalesce and so no longer show the typical shape of the mine. If a mined leaf is held up to the light, a spiral grooving can often be seen within the mine.

Although leaf mining damage may be considered unsightly, it is unlikely to affect the health or vigour of an established tree or shrub and 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.