Effect of (+)-limonene and 1-methoxy-2-propanol on Ips typographus response to pheromone blends

We compared two different strategies to increase the catches of Ips typographus (L.), particularly males, in pheromone-baited traps, The first of these strategies, the barrier approach, used alternating pheromone blends, targeting males and females respectively, in closely-spaced traps forming a barrier around forest stands. The second strategy, the single trap approach, used widely-spaced traps that were all baited with the same lure and intended to trap the highest possible numbers of males without compromising trapping of females. In the blend used for the barrier traps targeting primarily males, with a lower percentage of (4S)-cis-verbenol (cV), the ( )-[alpha]-pinene was replaced step wise with (+)-limonene at rates of 0%, 1%, 10%, 35%, 60% and 90%. This replacement had no significant effect oil the numbers of responding L. typographus males, but there was a slight effect oil the percentage of males caught. In the attractant blend for the barrier traps targeting females, with a higher percentage of cV, the 2-methyl-3-buten-2-ol (MB) was replaced with 1-methoxy-2-propanol (MP) in a similar fashion as for the male-specific blend. The replacement did not significantly affect the catch of females. Thus, it is Possible to use the MP in the blend with eV and ipsdienol without significant change in catch efficacy. In the blends for single traps, the ( )-[alpha]-pinene was replaced with (+)-limonene and MB with MP. The replacement of ( )-[alpha]-pinene had only a slight effect oil the percentage of males, but the results suggest that replacing MB with MP in the blend will not significantly reduce trapping efficacy.