Quantification of 2-butanol as a sex attractant pheromone and related alcohols emitted by individual white grub beetle, Dasylepida ishigakiensis (Coleoptera: Scarabaeidae)

Abstract

Females of the white grub beetle, Dasylepida ishigakiensis, emit a highly volatile, hydrophilic sex pheromone 2-butanol and related compounds. To quantify these compounds, a new method using water to trap them was developed. Vapors of 2-butanol, 2-propanol and ethanol were trapped with water, extracted with an SPME fiber and then injected into GC-MS for analyses. Quantification curves of each alcohol showed good linearity within a certain range. The recovery rate of 2-butanol released from authentic lure tubes was estimated to be ca. 70%. These results indicated that the method tested would be applicable to measure the amounts of volatiles emitted by the beetles. Using this method, it was estimated that field-collected calling females emitted more than 200 ng 2-butanol, ca. 50 ng 2-propanol, and ca. 500 ng ethanol on average in the laboratory. In a second calling trial, however, the amount of 2-butanol emitted by females was reduced to 3% of the amount in the first calling trial. Trace amounts of 2-butanol were detected in volatile samples from males. Because 2-propanol and ethanol were emitted by both sexes in similar amounts, they may not be involved in sexual communication.