Response of four American engraver bark beetles, Ips spp. (Col., Scolytidae), to synthetic racemates of chiral pheromones
1994
Kohnle, U. (Freiburg Univ. (Germany). Forstzoologisches Inst.) | Vite, J.P. | Meyer, H. | Francke, W.
The enantiomer composition of terpene alcohol pheromones produced by host selecting males of 4 American Ips spp. was determined as (S)-(-)-ipsenol (above 99% S--) in Ips grandicollis, as (S)-(+)-ipsdienol (90% S-+) in Ips avulsus, as an enantiomer mixture of 77% (R)-(-)- and 23% (S)-(+)-ipsdienol in Ips calligraphus calligraphus and as (S)-(+)-ipsdienol (above 99% S-+ and (S)-(-)-ipsenol (99% S--) in Ips paraconfusus. Field experiments were carried out to investigate the beetles' response to baits containing different concentrations of commercial (+-)-ipsdienol and (+-)-ipsenol, respectively. The tests revealed the following response pattern: a) I. c. calligraphus catch numbers increased with (+-)-ipsdienol concentrations but were reduced by (+-)-ipsenol; b) in contrast, I. grandicollis response was reduced by (+-)-ipsdienol but enhanced by (+-)-ipsenol; c) I- avulsus catch numbers increased with concentrations of racemates of both terpene alcohols; d) I. paraconfusus barely responded to traps baited with the synthetic racemates. The later phenomenon obviously was based on the inhibitory effect of non-natural (R)-(-)-ipsdienol which rendered the racemic test material an inhibitor for I. paraconfusus
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