Subject matter of the present invention is a suspension concentrate composition comprising an a) isothiazoline insecticide and b) activated charcoal, wherein the composition is substantially free of a non-polar solvent. The invention further relates to a process for the preparation of said composition; a suspension obtainable by mixing water, an isothiazoline insecticide and activated charcoal; and to a method for controlling undesired attack by insects or mites, where the suspension concentrate composition or the suspension is allowed to act on the respective pests, their environment or on the crop plants to be protected from the respective pests.