Boxwood Leafminer

Boxwood leafminer adults will be emerging any day. The maggots can do significant damage to the appearance of boxwood, but they usually do not cause dieback. Because the boxwood leafminer has only one generation of midges per year, treating in April and May with a systemic insecticide may prevent premature plant defoliation. Another application should probably be made in mid to late February of the following spring. The maggots develop in blister-like galls on the current year's leaves. Heavily-infested shrubs may become discolored particularly during the winter. These shrubs also tend to defoliate prematurely. In our demonstrations, Orthene and Merit have both given good control of this leafminer when injected into the soil or applied as a drench. Orthene 9.4% emulsifiable concentrate is actually labeled for leafminers on shrubs. Merit is labeled for leafminers on ornamentals and now being marketed in several homeowner products. Ornamentals and Turf Insect Note No. 16 (http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/ort016e/ort016e.htm) provides information on the biology and control of the boxwood leafminer.

From: Steve Bambara, Extension Entomologist