Holly Leafminer: Appearance, Territory, Damage and Life Cycle

Latin Name: Phytomyza Ilicis

Appearances: P. Ilicis, the holly leafminer, only eats English hollies. Both have a little black fly that is about 1/8 inch long as an adult, and the larva, a maggot, tunnels through the leaves, leaving yellowish or brown twisting trails or blotches. It’s also possible for leaves to become twisted and flecked with tiny brown spots. Adult leaf miners have a similar appearance to house flies. They’re about a tenth of an inch long on average. In addition to being black or grey in colour with yellow stripes and clear wings, they are also black or grey in colour. Larvae resemble small worms or maggots, measuring about 13 inches long and tinted green or pale yellow.

Host Plants: Only the leaves of American holly is eaten by the native holly leafminer. The native holly leafminer, for example, feeds exclusively on the foliage of American holly, Ilex opaca, and its cultivars. The holly leafminer is another leafminer found on plants of the Ilex genus.

Territory: They are native to North America, Europe, and they were introduced to America.

Damage Caused: Small raised lumps on the leaf where the female has implanted the egg are the first signs. Females and mature males feed on the delicate liquid inside the leaves through feeding punctures, which are small pinpoint holes in the leaves. This injury is sometimes mistaken for damage caused by leaf spines, which can similarly puncture leaves. When the baby maggots hatch from the eggs, they eat in light green serpentine tunnels that widen as the maggot grows. The maggot may have mined an area that looks like a patch or blotch in later stages.

Life Cycle and Habits: In June, the small adult leaf-miner flies lay their eggs at the base of the leaf’s midrib on the underside. Further feeding results in the formation of meandering mines, which reach their peak size in March. From March to May, larvae pupate under the cuticle of the last larval stage. Adult moths are most active in the morning and evening, resting on the undersides of leaves throughout the day. They are rarely seen during the day. Each year, only one generation happens. The larvae spend the winter in the tree’s leaves or fallen leaves. Adults emerge between mid-May and late-June, and begin laying eggs after about ten days. The females cut a slit in the leaf and lay their eggs inside. When the larva hatches, the young start eating the leaf tissue.