English holly, Ilex aquifolium, is the only host of this leafminer. Adults of this leafminer are small black flies about 3mm long. Larvae are similar in length but of a yellowish brown color. Eggs are usually laid in the midrib or leaf margin where early mining occurs. Adult females puncture new holly leaves to feed on the juices of the tender growth. Adults become active on new terminal leaves in May. There is one generation per year. The holly leafminer produces snake-like mines on leaves of the English holly. Young larvae tunnel into the leaf vein until late fall and only then does the linear, yellowish-green mine become obvious on the leaf surface. Heavy infestations can cause premature leaf drop, and can greatly hinder the health of the plant. Mines begun the previous summer begin to expand as yellowish-brown patches in early spring. Look for short, newly forming mines in late summer.
Holly Leafminer
