PURPOSE: To obtain a controlling agent effective against various pests, esp. Psychodidae and Phoridae, breeding from or living in purification tanks and other wastewater disposal facilities.

CONSTITUTION: This controlling agent contains, as active ingredient, N-(2,6- difluorobenzoyl)-N-]3,5-dichloro-4-(3-chloro-5-trifluoromethyl-2-pyridyloxy) phenyl]urea. This agent has extraordinarily excellent effect, at low doses, for controlling and preventing the breeding of the larvae, pupae and imagoes of Psychodidae and Phoridae, its dose being 0.001-1000ppm in terms of the level of the active ingredient. This controlling agent can further be formulated with at least one kind of agent selected from insect growth inhibitors, pyrethroid- based insecticides, pyrethroid-like insecticides, organophosphorus-based insecticides, carbamate-based insecticides and chloronicotine-based insecticides, and a synergistic agent such as octachlorodipropyl ether or isobornylocyanato acetate.