INHIBITORY EFFECT OF (-)ALPHA-PINENE HIGH RELEASE RATES ON IPS TYPOGRAPHUS (L.) RESPONSE TO ITS AGGREGATION PHEROMONE

The aim of the research presented in this paper was to prove that the effect of (-)alphapinene on the response of Ips typographus (L.) to its aggregation pheromone depends on the release rates of both pheromone and monoterpene volatiles. Six treatments have been tested in four experimental areas using six replicates for each treatment: V1 – pheromone + (-)alpha-pinen 200 mg/day, V2 – pheromone + (-)alpha-pinen 500 mg/day, V3 – pheromone + (-)alpha-pinen 2000 mg/day, V4 – pheromone, V5 – control (blank) and V6 – 1/3 pheromone dispenser with 1/3 of normal release rate. In all experimental areas, most captures have been recorded at V4 (pheromone alone), while alpha-pinene at cca. 200mg/day, 500 mg/day and 2000 mg/day caused the decrease of the captures by 13.2-43.9%, 22-55.2% and 53.1-70.2% respectively. The traps baited with pheromone dispensers which were conditioned to have a release rate equal to only 1/3 from the release rate of the commercial dispensers, caught insects representing about 1/3 of those recorded at the traps with normal dispensers. The results confirm the hypothesis that the response of Ips typographus beetles to the combination of synthetic pheromone with (-)-alpha-pinene depends on the concentration of volatile substances that are released around the source, respectively on the release rates of the pheromone and monoterpene. They also demonstrate, that at high release rates of the pheromone (cca. 30 mg/day), (-)alpha-pinene released at a rate of 200-2000 mg/day has an inhibitory effect, determining the decrease of the number of beetles that are caught in the pheromone traps.