184 - Variation in efficacy of essential oils deployed as spatial repellents

Spatial repellents are a desirable alternative to pesticides for myriad reasons.  They protect groups from nuisance and disease-transmitting vectors, rather than individuals.  Due to the nature of their deployment, they are a passive method of repelling mosquitoes.  Nothing further is required after initial setup as long as the repellent remains efficacious.  There is no need to remember to apply or re-apply.  Furthermore, there is little selective pressure to induce resistance to a spatial repellent due to the presumption that they do not cause mortality.  Essential oils can take this desirability further if they are proven to be efficacious.  They are seen as “natural,” are potentially safer than traditional repellents, and may therefore be more accepted by the general populace.  We attempted to determine the efficacy of five essential oils (Cassia, Cognac, Origanum, Patchouli, and proprietary “Essential Oil Z”) against a control when deployed in the field.  Six CDC light traps were set in a wooded area, far enough from each other to ensure the treatments did not interfere with one another.  The rain shields of the traps were modified so that eight cotton balls could be wrapped in tulle and hung with a clip along the outside rim of the shield.  Traps were baited with CO2 and run for 24 h with cotton balls treated with an essential oil or control.  Each treatment was rotated through all trap locations to account for differential catch due to location.  All rotations were set multiple times with the same treated cotton balls to determine if efficacy remains after weathering.  After trapping was concluded, all collections were identified and tallied to species, and the percent reduction in collections for each treatment relative to the control was calculated.  We discuss differences in total numbers collected, as well as differences in total numbers of individual species.