Abstract: An insecticidal formulation based on Ocimum gratissimum essential oil and montmorillonite clays was develop for maize protection. The insecticidal effects of formulations based on Ocimum gratissimum essential oil and montmorillonite have been improved after modifications of the clay by CTMA in relation to their higher sorption capacity. Insecticidal tests have been conducted against the maize weevil Sitophilus zeamais. The insecticidal effects of the essential oil persisted for about 7, 45 and 110 d, respectively for crude essential oil after adsorption on unmodified and modified clay. The findings suggest that formulations based on essential oils and modified clays should be considered as alternatives to synthetic insecticides for use in pest control of stored products.