ESSENTIAL OIL ANALYSIS AND FIELD-EVALUATION OF THE CITROSA PLANT PELARGONIUM-CITROSUM AS A REPELLENT AGAINST POPULATIONS OF AEDES MOSQUITOS

A plant recently introduced into North America as the citrosa, Pelargo nium citrosum ('Van Leenii'), has been marketed as a biological repell ent against mosquitoes. Citrosa is claimed to repel mosquitoes within a 10 ft.(2) (0.93 m(2)) area due to a continuous fragrant release of c itronella oil. The total essential oil yield was 0.2 +/- 0.1% from fre sh plant material. Chemical analysis by the authors revealed that comb ined essential oils of fresh greenhouse- and field-grown citrosa have 35.4 +/- 6.2%, geraniol, 10.4 +/- 1.6% citronellol, 8.9 +/- 2.0% isome nthone, and 6.8 +/- 3.8% linalool. Both the morphology and essential o il of citrosa fall within the Pelargonium x asperum hybrid complex and are similar to 'Rose', the commercial rose geranium. No character of morphology or essential oil of a Cymbopogon species yielding commercia l citronella oil could be detected in the citrosa. The effectiveness o f the citrosa as a repellent against field populations of spring Aedes spp, mosquitoes was evaluated and compared with a 75% deer (N,N-dieth yl-3-methylbenzamide) formulation. Deet provided >90% reduction in mos quitoes biting subjects for up to 8 h post-treatment. There was no sig nificant difference between citrosa-treated and nontreated subjects.