AbstractThin‐layer chromatography was used to assess semi‐quantitively the persistence of six organophosphorus insecticides in hen‐house litter. Malathion disappeared within 4 h of application. Carbofenthion was the most persistent. Four weeks after treatment the proportions of the applied doses extracted from the litter were: carbofenthion 46%, phorate 21%, diazinon 13%, coumaphos 7% and fenitrothi