Improvement of Ips typographus catches in pheromone trap barriers by altering of sex assigned pheromone blends

The present study was based on the idea of a pheromone trap barrier with alternating dispensers releasing different pheromone mixtures that affect males and females differently. We tested the possibility of increasing the catch efficacy of pheromone trap barriers by altering the pheromone mixture with low levels of cis-Verbenol (cV, targeting males, BM), the mixture with high levels of cV (targeting females, BF) and the pheromone mixture with intermediate levels of cV (SL). In addition, we were interested in lowering the dispersion of attracted bark beetles, especially males, which reduces the risk of attack on trees in the surroundings. Significant highest absolute and relative catch was found in the catch of the combination BM–BF, which was 2.2-fold higher than the catch of the control barrier treated with commercial IT Ecolure baits (Fytofarm, Slovakia). At the same time, the lowest dispersal in the surroundings of the barrier with the combination BM–BF was found, which was 2.5-fold lower than in the control barrier. The performance of the BM–BF combination of mixtures was proved in a field trial experiment where the total season catch of the part of the barrier treated with BM–BF dispensers caught 1.5-fold more beetles during the season than the control part treated with IT Ecolure dispensers. Furthermore, the results confirm that the performance of the combination of low levels of cV (targeting males) and high levels of cV (targeting females) is complemented by the desired reduced dispersion around the barrier, which reduces the risk of attack on trees in the surroundings.