Contact Toxicity of Hypericum Extracts against Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae)

Abstract

Medicinal and aromatic plants have popular recently to investigate their usability as natural resources in many areas due to their superior biological activity properties. Hypericum genus contained important medicinal plant species known worldwide. In this study, the ethanol extracts from different plant parts (flower, leaf and stem) of three Hypericum perforatum, Hypericum heterophyllum, Hypericum scabrum were screened for their toxicity against adults of Rhyzopertha dominica (Coleoptera: Bostrichidae), an important insect of stored grains in many regions of the world. Insecticidal activity was analysed at 10 % concentration of ethanol extracts, and measurements were taken at three different exposure times (24, 48 and 72 hours). Considering the factors analyzed on this insect, Hypericum species, plant part, exposure time as well as the interaction of Hypericum species and plant part displayed a statistically significant effect. The mortality values of extracts from H. perforatum, H. heterophyllum and H. scabrum varied from 44.8 % to 88.9 %, 26.0 to 78.8 %, 26.1 % to 50.3 % for adult of R. dominca, respectively, after 72 h. H. perforatum showed a stronger effect than other species. Among plant parts, the leaf showed superior mortality on this insect. In addition, the mortality rate increased with increasing exposure time. According to the interaction between Hypericum species and the plant part, the leaf of H. perforatum (79.4 %) displayed the strongest mortality, followed by the leaf of H. heterophyllum (70.6 %). After 72 hours, the highest mortality was recorded in the leaf parts of H. perforatum. The current results showed that the extracts, in particular, the leaf extracts of H. perforatum and H. heterophyllum, may be evaluated as a new natural potential product of plant-derived insecticide because of its high mortality impact against R. dominica.