WHATEVER ELSE the city's residents may find wrong with the services rendered or not rendered by the D.C. government, a salute of some proportions goes to Mayor Barry for declaring serious war -- complete with airborne weekend warriors from city hall on bombing missions over upper Northwest -- against the legitimately dreaded gypsy moth. Had it not been for Capt. Barry's series of early morning raids on the treetops in seriously infested neighborhoods of the city, hundreds of large trees on public as well as private space would have been fatally defoliated by what is considered the most serious threat to the health of oak and other hardwood trees.

Most of the fanfare this summer, of course, was for and about the cicada, whose 17-year absences make each return a special event. But in those neighborhoods that suffered invasions of the gypsy moth caterpillars last summer, the cicada's rites of passage were a sideshow. Had the caterpillars sunk their choppers into the same trees this season, experts say the trees probably would not have survived.

But early this year, the D.C. Department of Public Works, in cooperation with the University of the District of Columbia Cooperative Extension Service, mapped out areas for aerial spraying and scheduled sorties for those moments when the caterpillars would be fully hatched and starting to feed. The spray ordered was a bacterial insecticide deemed unharmful to humans or other mammals. Then in the dawn hours of spring, they bombed and rebombed.

Reports from the front have been good. In areas totally taken over last year, few if any grown caterpillars were seen, and those few that were wound up trapped in little burlap and plastic skirts that the city and residents wrapped around tree trunks. While no one knows what evil lurks in these areas for next summer, every area resident who treasures Washington's trees can be thankful that the city won a big war in 1987.