Pest description and crop damage This species of holly leafminer feeds only on English holly (Ilex aquifolium). The adult is a small, grayish black fly that emerges throughout May. Larvae are yellowish and about 0.0625 inch long. Characteristic damage by larvae includes the presence of yellow, brown, or reddish mines on the leaves. Initially, the mines are fairly narrow and winding, but become large blotches as the larvae overwinters in the leaf. The upper and lower leaf surfaces remain after feeding but are separated easily.
Biology and life history The insect overwinters as a larva in the mined leaf. It pupates in early spring, and adult flies emerge in May. A few days later, females begin laying eggs on the undersides of leaves in the midvein. The eggs hatch, and the larva burrows into the leaf and commences making the mine. They continue mining through the late fall. There is one generation per year.
Hand-pick and destroy infested leaves in the fall.
Apply just before bloom.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 206).