262 - Preliminary evaluation of toxicity of essential oils to Aedes taeniorhynchus.

There are many studies published in the scientific literature reporting the results of trials of essential oils against larvae of Aedes aegypti.  The potential of two essential oils, Melissa oil (Melissa officinalis L.) and Rosemary oil (Salvia rosmarinus Spenn), to kill larvae of Aedes taeniorhynchus was investigated.  A stock solution of 0.05% Tween® 20 was prepared and used as a diluent for all tests.  Tween® 20 is an emulsifying agent used to prepare stable oil-in-water emulsions.  A range of dilutions (1% to 0.001%) was prepared for both oils.  Distilled water and the stock Tween® 20 solution were used as negative controls; a 0.1% solution of naled was used as a positive control.  Over 2/3 of larvae tested died at the lowest concentration of Melissa oil whereas none died at the same concentration of Rosemary oil.  There was zero mortality in the distilled water and Tween® 20 negative controls and 100% mortality in the naled positive control.  Based on limited trials, Melissa oil appears to be more toxic to Aedes taeniorhynchus larvae than is Rosemary oil.  More trials are planned.