Chemical Composition of Rose-Scented Pelargonium Essential Oils and Their Biting Deterrence and Insecticidal Activity

Rose-scented Pelargonium essential oils from the varieties 'Bourbon', 'China', 'Egypt' and two cultivars from South Carolina: 'Rober's Lemon Rose' and 'Frensham' were analyzed by gas chromatography (GC-FID) and gas chromatography – mass spectrometry (GC-MS). A total of 136 different compounds were identified from the five Pelargonium oils and the percentage of compounds characterized ranged from 85.5–99.7%. All the oils showed mosquito biting deterrent activity against Aedes aegypti. Biting deterrent effects were similar at 10µg/cm2 and at 100µg/cm2 among the oils. Among the pure compounds only geranic acid showed activity which was similar to Deet at 25 nmol/cm2. All oils killed 100% Ae. egypti larvae at 500 and 250 ppm and trans-nerolidol was the most active compound at 31.25 ppm with 80% mortality. There was no adult mosquito mortality for these oils at 3.125µg per mosquito. All five Pelargonium oils and pure compounds showed insecticidal activity against adult azalea lace bugs Stephanitis pyrioides and all oils were more active than the commercial insecticides malathion and neem, 10mg/mL. These data show that some of Pelargonium oils and/or their active ingredients could be used as mosquito biting deterrents and agrochemical agent for azalea lace bugs. Acknowledgements. This study was supported by a grant from the Deployed War-Fighter Protection (DWFP) Research Program and the U.S. Department of Defense through the Armed Forces Pest Management Board (AFPMB) and USDA, ARS grant No. 56–6402–1-612.