Larvae of several families of small moths are the most common foliage-mining pests in landscapes. Larvae of other insects, including sawflies and wasps, also mine some plants, feeding inside leaves, needles, shoots, or buds. Each kind feeds on only one or several closely related plants. The host species and characteristic form of the larva's damage help to identify the insect species. Mature larvae of azalea leafminer feed externally, webbing leaves together with silk. Juniper webworms mine needles when young and feed externally in webbing when mature.Other groups of foliage miners include cypress and arborvitae foliage miners, casemakers and skeletonizers, shield bearers, and pine tip or shoot moths.
Damage
Foliage-mining insects cause off-color patches, sinuous trails, or holes in leaves. Portions of a leaf or patches of foliage may turn yellow or brown and die back. Larvae may be seen dropping from foliage on silken threads. Severe infestations can slow plant growth; established woody plants tolerate extensive foliage mining and are rarely if ever killed.
Solutions
Provide proper care, especially irrigation, to keep plants vigorous. Prune out and dispose of foliage infested with larvae to restore the plant's aesthetic appearance and provide some control. Plant resistant species or varieties. If planting birch, plant least susceptible species. Some foliage miners can be controlled by natural enemies; conserve beneficials by avoiding broad-spectrum persistent insecticides.
