Leafminers are the larvae of small insects, which make tunnels in the leaves of many types of plant, especially chrysanthemums, lilacs (Syringa), hollies (Ilex) and apples.

Control

The larvae are difficult to kill once they are in their tunnels, and the easiest way to deal with them is to remove affected leaves. If the infestation is severe, spray with pirimiphos-methyl, dimethoate or HCH. Alternatively, parasitic wasps may be used as a biological control.