Evaluation of natural compounds for insect repellent packaging: laboratory and semi-field experiments with pests of cereal products

This work aimed at identifying natural substances with a repellent effect on insect pests of cereal products, to be used in repellent packaging in semi-field experiments simulating insect attacks in storage rooms. Initially, the repellence of different concentrations of selected natural compounds was evaluated on groups of 10 adults of Sitophilus oryzae, Rhyzopertha dominica, Stegobium paniceum, and 5 larvae of Plodia interpunctella, using Petri dishes with treated/untreated cardboard disks halves. Then, the performance of repellent cardboard boxes subjected to repeated mixed insects attacks was evaluated in storage room conditions. The boxes, obtained by applying paints with microcapsules of essential oils of garlic and/or rosemary (the most repellent after the first test), were handmade simulating commercial pasta packages and were filled with 500g pasta. The boxes were placed in couples (with different combinations that included untreated control) inside fenestrated plastic containers with groups of 20 insects (5 adults of S. oryzae, R. dominica, Lasioderma serricorne; 5 larvae of Ephestia spp). Every month, insect mortality inside the containers was checked and new groups of insects were introduced. After 3 months all the cardboard packages were opened and the number of insects inside and outside the boxes was recorded. The best results were obtained in presence of garlic essential oil. The criticalities emerged in the view of practical applications are discussed.