A Male-Associated Aggregation Pheromone of Cyrtogenius luteus, An Invasive Bark Beetle in Southern South America

Bark beetles are among the most important invasive pests affecting pine forestry worldwide, yet the chemical ecology of many introduced species remains largely unknown. Cyrtogenius luteus is an invasive scolytine established in pine plantations in South America, for which no pheromone had previously been identified. Here, we report the identification and biological evaluation of a male-associated aggregation pheromone in C. luteus. Volatiles from male-infested, female-infested, and unattacked Pinus taeda wood were collected and analyzed by thermal desorption GC-MS. A compound consistently detected only in male-infested pine wood was identified as p-mentha-1,8-dien-4-ol through comparison with a synthetic standard. In Y-olfactometer assays, both males and females were attracted to volatiles from unattacked pine relative to clean air and showed a significant preference for male-attacked pine over unattacked pine, as indicated by both first choice and residence time. Field trials with synthetic p-mentha-1,8-dien-4-ol confirmed its biological activity: cross-vane traps baited with a combination of synthetic p-mentha-1,8-dien-4-ol and host attractants increased adult captures more than 20-fold, in comparison with the conventional host-attractant baited traps. Males and females were captured in similar proportions. Together, the male-specific occurrence of p-mentha-1,8-dien-4-ol, the attraction of both sexes to male-attacked host material, and the response of both sexes to the synthetic compound in the field, identify the racemate of this oxygenated monoterpene as a male-aggregation pheromone of C. luteus. This is the first pheromone structure reported for the species and provides new insight into the chemical ecology of an invasive bark beetle established in South American pine plantations.