Sex Pheromone of the Papaya Mealybug

Sex pheromones of mealybugs are reported from more than 20 species and have generally been shown to be monoterpene alcohols esterified with short-chain carboxylic acids. Here, however, we discovered and isolated an alcohol without an acid moiety as a pheromone compound released from adult females of the papaya mealybug, Paracoccus marginatus. By means of gas chromatography - mass spectrometry and nuclear magnetic resonance spectroscopy analyses, the structure was identified to be trans-2-(2-isopropenyl-1-methylcyclobutyl)ethanol, a monoterpene with a unique cyclobutene skeleton, commonly known as fragranol. We then completely separated synthetic (±)-fragranol into each enantiomer by means of preparative high-performance liquid chromatography using a chiral resolution column, and (-)-(1S,2S)-fragranol was definitely confirmed to be the natural pheromone and to attract many males in the field when used as a pheromone trap lure. (±)-Fragranol showed attractiveness comparable to that of the pure (-)-(1S,2S)-enantiomer. This study provides not only useful information for the monitoring and management of P. marginatus but also an interesting exception underlining the great diversity of mealybug pheromone structures.