Abstract :
The lesser grain borer, Rhizopertha dominica Fabricius and the red flour beetle, Tribolium castaneum Herbst, are of the most insect species which cause the highest grain damage. Many chemical insecticides related to different groups used as protectants to stored products presented serious problems to human health and environment. To avoid these disadvantages, laboratory experiments were carried out to evaluate two materials namely, plant oil (Orange oil) and bioinsecticide, spinosad as stored wheat grain protectants against T. castaneum and R. dominica using two bioassays technique, mixing with medium and repellency at different exposure periods (72 h for mixing with feeding medium and 24 h for repellency). Results obtained revealed that the two tested materials, orange oil and spinosad had moderately action on the two tested insects either by mixing with medium or by repellent bioassay methods. Data cleared that the effect of the tested materials increased with the increasing of concentration and period of exposure especially with mixing bioassay. For repellent effect, the highest level of concentration had the most action on both T. castaneum and R. dominica. Except orange oil against T. castaneum the effect of materials tested decreased through 24 h of exposure. Spinosad showed nearly similar effect on the two tested insects while R. dominica was found to be more tolerant than T. castaneum with orange oil. Finally, our findings suggest that spinosad and orange oil may to be potential protectants against R. dominica and T. castaneum in stored wheat grain principally with mixing bioassay technique.
