Identification of the Sex Pheromone of the Spherical Mealybug Nipaecoccus viridis

The spherical mealybug Nipaecoccus viridis is a pest of several major crops including soybeans, grapes and citrus varieties. Sessile virgin females of N. viridis release two volatiles, 2,2,3,4-tetramethyl-3-cyclopentene-1-methanol (γ-necrodol) and γ-necrodyl isobutyrate, on a circadian rhythm with peak at 17:00 (11 hr of photophase) as determined by automated, sequential solid phase micro extraction with gas chromatography-mass spectrometry analysis. The females increased the released amounts with age by about seven-fold from 5 to 6 d to 10-12 d of age. trans-3,4,5,5-Tetramethyl-2-cyclopentene-1-methanol (trans-α-necrodol) and trans-α-necrodyl acetate, found in essential oil of Spanish lavender, Lavandula luisieri, were rearranged to γ-necrodol and then used to synthesize γ-necrodyl isobutyrate. GC-MS and NMR data confirmed the identifications. In a petri dish bioassay, N. viridis males were significantly attracted to filter paper discs impregnated with γ-necrodyl isobutyrate but not to γ-necrodol or controls. A mixture of the two compounds was not more attractive than γ-necrodyl isobutyrate alone. Similar results were obtained with trapping flying adults, suggesting that the sex pheromone consists only of γ-necrodyl isobutyrate. This compound has not been reported previously in insects. Conversion of α-necrodol in lavender essential oil simplifies the synthesis of the sex pheromone and should allow its use in management of this cosmopolitan invasive pest.