Field response of the six‐toothed pine bark beetle, Ips sexdentatus (Col.: Curculionidae, Scolytinae), to pheromonal blend candidates

Abstract The identification and description of the chemical signals involved in the aggregation of bark beetles may lead to the development of integrated pest management strategies using synthetic pheromones. Ips sexdentatus Boern. (Col.: Scolytinae) colonizes trees of the Pinus genus across Europe, causing severe damage in occasions. The effect of cis‐verbenol, ipsenol, 2‐methyl‐3‐buten‐2‐ol (MB) and myrtenol in relation to the major pheromonal compound ipsdienol on the aggregation behaviour of I. sexdentatus was studied on four field bioassays. The ternary blend of racemic ipsdienol, cis‐verbenol and racemic ipsenol consistently caught the highest number of bark beetles, resulting in large standardized mean differences (dunbiased > 0.8). The binary blends between ipsdienol and ipsenol, and ipsdienol and cis‐verbenol also improved the performance of ipsdienol, although only ipsenol did it significantly. On the other hand, catches were reduced (dunbiased = −0.96) when MB was released along ipsdienol, although the effect was found to be non‐significant. On a third bioassay, the relative release rates between ipsdienol, ipsenol and cis‐verbenol were studied. Although no differences were found between the ternary blends, a ratio of 1 : 0.25 : 0.5 for ipsdienol, ipsenol and cis‐verbenol, respectively, scored the strongest effect size (dunbiased = 1.17). A fourth bioassay studied the behavioural effects of myrtenol and found no significant modifications to previously established findings. Myrtenol on its own attracted almost no individuals of I. sexdentatus. High numbers of bark beetle predators Thanasimus formicarius L. and Temnochila caerulea Olivier were trapped during the trials. The binary blend between ipsdienol and ipsdienol was shown to catch the highest significant amount of T. formicarius, whereas numbers of T. caerulea caught were highest on the binary blend between cis‐verbenol and ipsdienol. Presented results establish the ternary blend between ipsdienol, ipsenol and cis‐verbenol as a reference functional aggregative lure ready to be used on the management of I. sexdentatus.