EcoBio-Block S, a novel controlled release system (CRS) for the insect growth regulator pyriproxyfen, uses a water-purifying concrete block system (EcoBio-Block) composed of a porous volcanic rock and cement, and it incorporates the aerobic bacterial groups of Bacillus subtilis natto. EcoBio-Block S showed high inhibitory activity against mosquito emergence as well as a water-purifying effect. Chemical analysis and bioassay showed that EcoBio-Block S provides a high-performance CRS that controls the release of pyriproxyfen at low levels according to "zero order kinetics".