Pest description and crop damage The adult is a small (0.1 inch) orange to yellow fly which emerges in early May. The larval stage of the boxwood leafminer is a small yellow to green maggot found inside the mined leaves. Leafminers feed by removing green tissue from between the upper and lower leaf surfaces. Feeding by leafminers can be detected by the presence of yellow to brownish blotch-like mines or by a blistered, thickened appearance of the leaves. Damage is mainly aesthetic, but repeated severe infestations may damage shrubs.
Biology and life history The insect overwinters as a larva in the mined leaves. In spring, it becomes active and grows rapidly. The orange pupae can be seen clinging to the leaf before the adult fly emerges. Female flies lay eggs on the upper surface of the current season's growth. The larvae hatch and mine the leaves through the summer. There is one generation per year.
Pick off infested leaves or clip out infested terminals. Plant resistant varieties, which include 'Suffruticosa', 'Pendula', and 'Argenteo-variegata'.
- abamectin (Avid)-Apply when adults are laying eggs.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 204).
PNW Nursery IPM: Boxwood leafminer (http://oregonstate.edu/dept/nurspest/boxwood_leafminer.htm)