Effects of natural compounds on stored product pests evaluated by repellency and perforation ability trials

In the view to develop an innovative system for the prevention of insect damages to food packs, repellency and perforation ability tests were performed to evaluate the effects of two essential oils (basil and vetiver) and of an azadiractin based formulation on the stored product pests Rhizopertha dominica, Sitophilus oryzae, Tribolium castaneum and Stegobium paniceum. Repellency was tested by means of Petri dishes lined with filter paper where a half was treated with the test substance and the other half left untreated. The position of 10 insects was recorded after 1, 2, 4 hrs and repellency indexes were compared. Perforation ability trials were carried out using an especially designed apparatus where 5 insects had to perforate a paper layer treated with the test substance in order to reach the food. Latency to perforation and mortality were recorded. All substances were tested at 3 concentrations (1, 5, 10 ml/m2). From repellency trials emerged that vetiver oil was repellent for all species even at the lowest concentration; basil oil was attractive for almost all species except R. dominica; the azadiractin based product was slightly repellent for T. castaneum, slightly attractive for R. dominica and toxic to S. paniceum. Perforation ability trials were performed only on R. dominica, whose penetrating capacity was reduced by all substances, especially at the highest concentrations, and on S. oryzae, where only vetiver oil showed an evident inhibitory effect to perforation.