Biological effects of Arizona cypress, Cupressus arizonica against rice weevil, Sitophilus oryzae and sawtoothed grain beetle, Oryzaephilus surinamensis
Fumigant toxicity, repellency and durability of insecticidal effect of Arizona cypress leaves essential oil were investigated against adults of two Coleopteran stored product pests; rice weevil, Sitophilus oryzae L. and saw-toothed grain beetle, Oryzaephilus surinamensis L. The essential oil was extracted by Clevenger-type apparatus. The bioassays were conducted by using 40 ml glass vials as container and Whatman filter paper (1×2 cm) as the essential oil release source. Repellency effect was evaluated by comparing the number of adults in both treated and not-treated portions. The adult’s mortality was increased in consequence of raising the concentrations. The LC50 values of essential oil for these two pests were 456.3 and 235.3 µl/L air, respectively. Adults of sawtoothed grain beetle were more susceptible than rice weevil. The average repellencies of the essential oil against the insects were 72.5 and 94.16%, respectively. These repellencies were as grades of IV and V respectively, of the sextet classification. The essential oil persistence was different depending on the concentration and exposure time of the treatments. Based on the results, C. arizonica essential oil had acceptable efficacy for controlling these stored product pests.