a biologically active agent - containing composition is prepared by reacting an aqueous emulsion or dispersion of a suitable biologically active agent and an optional filler in an aqueous solution or gel of a polyhydroxy polymer and an inorganic salt , with a boric acid or boric acid derivative until an insolubilized matrix phase is formed having entrapped therein uniformly dispersed , discontinuous domains of said agent and an optional aqueous phase that can be separated from the matrix phase by decanting , filtration , or the like ; the product is then dried and ground to the desired particle size . the composition is applied to the soil or plants where the biologically active agent is slow released for controlling pests .