Pest description and crop damage A tiny midge, or fly, that develops in leaves, deforming them. There are multiple generations each year, as little as 3 to 4 weeks apart. Thornless varieties of honeylocust are especially subject to damage.
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 April. Another management tactic is to protect new foliage with insecticide. Horticultural oil applications applied to smother eggs have also proven efficacious. Sometimes repeat applications are needed, at 2 to 4 weeks, beginning late spring.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 466).
PNW Nursery IPM: Honeylocust pod gall midge (http://oregonstate.edu/dept/nurspest/Honey_Locust_Pod_Gall_Midge.htm)