The invention relates to a process for coating a solid, water-insoluble particulate matter, with a metal oxide comprising: (a) contacting the solid, water-insoluble particulate matter with an ionic additive and an aqueous medium to obtain a dispersion of said particulate matter having positive charges on its surface; (b) subjecting the particulate matter to a coating procedure comprising precipitating a metal oxide salt onto the surface of the particulate matter to form a metal oxide layer thereon to thereby obtain particulate matter coated by a metal oxide coating layer; (c) repeating step (b) at least 4 more times; and (d) aging said coating layer. The invention further relates to particles comprising a particulate matter coated by a metal oxide layer, to a use of the particles for topical administration, and to a method for preventing, reducing, or eliminating pests at a locus, using the particles.