Pest description and crop damage The adult midge lays its eggs inside the sepals of new flower and leaf buds. The tiny maggot that hatches feeds in these areas causing blackened tissue, tip abortion, and distorted flower buds. There are two peaks of damage: in late June/early July and late August/early September.
Buy in bare-root or rinse off and dispose of container media when new plant material is brought in during the time midges are overwintering. Cut out and destroy infected tips. There are some roses with more resistance to the midge.
There are several strategies to midge management. One strategy is to target the overwintering larvae with a drench application prior to the emergent of the adults in the spring. Another management tactic is to protect new foliage with insecticide. Sometimes repeat applications are needed, at 2 to 4 weeks, if damage continues.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 470).
PNW Nursery IPM: Rose midge (http://oregonstate.edu/dept/nurspest/rose_midge.htm)