Dispersion containing, in addition to water, 0.5 to 20 wt. % of hydrophobic silica, 0.01 to 10 wt. % of a gelling or viscosity-increasing additive, 0.1 to 1 wt. % of a preservative and 0 to 1 wt. % of a surface-active substance. It is prepared by a procedure in which the individual components are dispersed successively or together into the water and in this procedure the individual components are deaerated before and/or during the addition or the dispersion is deaerated during the individual dispersing steps. The dispersion can be employed as an insecticide.