Insecticidal effect of from three Hypericum species extracts against Rhyzopertha dominica, Sitophilus oryzae and Tribolium confusum

ABSTRACT The search for new plant natural products with insecticidal properties to control insect pests in agriculture has gained relevance in the past decades. The aim of the study was to investigate the insecticidal activity of extracts derived from flower, leaf, and stem of three Hypericum species (Hypericum heterophyllum, Hypericum perforatum, Hypericum scabrum) against the adults of three important stored grain insect pests namely; Sitophilus oryzae (Curculionidae), Rhyzopertha dominica (Bostrichidae) and Tribolium confusum (Tenebrionidae). The insects were incubated with the food under 10% concentration of Hypericum extracts and the mortality was recorded after 24, 48 and 72 h of exposure. The extracts of the Hypericum species and exposure time were found to have statistically significant effective against the three insect pests. After 72 h exposure, the mortality ranged from 4.3 to 94.1 % for all insects. Among tested insects, R. dominica was more susceptible than T. confusum and S. oryzae. Although desirable insecticidal effect against the insects were recorded from all the three Hypericum species, the leaf extract of H. perforatum was more effective on R. dominica, while the flower and stem of H. scabrum displayed high toxic effect on T. confusum and S. oryzae, respectively. The leaf extracts, of H. perforatum, in particular, may be used as source of new potential botanical insecticides against R. dominica in stored grains.