Bioassays of the repellent properties of essential oils from Monarda species in Oklahoma against Drosophila melanogaster

CHED 783

Tucker J. Harrison, npaiva@sosu.edu, Jeff B. Hill, and Nancy L. Paiva, nlpaiva@alum.mit.edu. Department of Chemistry, Computer & Physical Sciences, Southeastern Oklahoma State University, 1405 N 4TH AVE, PMB 4215, Durant, OK 74701
Native American tribes were reported to use Monarda punctata and Monarda citriodora plant preparations to repel insects and for medicine. Previous studies in our lab indicated that Monarda extracts were highly repellent to mosquitoes. To determine effectiveness against additional insects, an apterous (wingless) strain of Drosophila melanogaster was selected because its lack of flight greatly simplifies handling. To feed and lay eggs, these flies crawl on moist food. A bioassay chamber was designed that allowed flies to choose between dishes containing control diet or diet supplemented with test compounds. Bioassays indicated that diets containing as low as 10 uL of 32-fold diluted essential oil per gram were highly repellent. Monarda essential oils contained predominantly thymol and isothymol; bioassays confirmed that these pure compounds were repellent at low concentrations. Monarda preparations compared favorably to DEET and non-DEET commercial insect repellents. (Funding by NSF-EPSCoR OK Educational Outreach Program EPS-0132534 and NIGMS-SCORE 5S06-GM008003.)