The Chrysanthemum Leaf Miner is a tiny leaf-mining fly. They belong to a family called Agromyzidae, which encompasses over 2,500 species of fly, all of which feed on various plants.
Leaf-mining flies are rarely seen when adults. The larvae, however, are much easier to observe. Leaf-mining larvae tunnel through the inner tissues of foliage, leaving a unique trail, or mine, behind.
The larvae of Chromatomyia syngenesiae mine the leaves of Chrysanthemum, Gazania, Senecio cineraria and Argyranthemum.
In most cases, the damage is only aesthetic, with healthy plants tolerating light to moderate infestations.
Plants kept under glass should be checked for damage all year around, and outdoor plants in the summer and autumn.