Abstract
Maize and wheat treated with malathion was stored in sealed jars for 6 months and analysed monthly for malathion and its derivatives. Dimethyl phosphorothiolothionic acid, malathion mono‐acid and malathion di‐acid were identified by thin‐layer chromato‐graphy, but malaoxon and its corresponding derivatives were not detected. The breakdown of malathion under these conditions appears to be hydrolytic rather than oxidative, or both.