Shug from Ny writes
Apply Gentrol IGR to areas of fly breeding as directed only. For drains, apply into and around the downspout and catch basin area. Coat these areas thoroughly as fly larvae develop in the scum buildup on the side of drain pipes. Repeat applications at 2 to 4 week intervals depending upon the severity of infestation. For more information on treating drain flies, please read our treatment article on How to Get Rid of Drain Flies.
Answer last updated on: 01/16/2021