Recapture of Ips typographus L. (Col., Scolytidae) with attractants of low release rates: localized dispersion and environmental influences

ABSTRACT

 

Abstract

1 The dispersal of Ips typographus L. (Col., Scolytidae) was studied using a mark–release–recapture approach in a grid of traps equipped with pheromone lures of release rates of about 8.4 mg/day of 2-methyl-3-buten-2-ol (MB) and 0.29 mg/day of (S)-cis-verbenol (cV) in experiment 1, and 1.2 mg/day of MB and 0.04 mg/day of cV in experiment 2.

2 We investigated whether beetle dispersal reflected the simple diffusion pattern observed in previous I. typographus experiments, for which attractant release rates generally approached 50 mg/day of MB and 1 mg/day of cV. We also examined how environmental parameters (wind) and human activities (felling) could influence the beetles' flight.

3 The recapture percentage was higher in experiment 1 than in experiment 2: respectively, 7.0% (with 64 traps) and 2.3% (with 100 traps) of the beetles that took off were caught in the traps.

4 With the higher release rate (experiment 1), trap catches decreased with increased distance, whereas with the lower release rate (experiment 2), trap catches rose between 50 and 100 m then decreased with increasing distance.

5 Flight was little orientated by prevailing wind directions, a feature probably explained by the low wind speeds (0–1.2 m/s) observed throughout the study.

6 High trap catches of unmarked beetles close to areas undergoing thinning activities suggest that the presence of freshly cut spruce and larch material could have an influence on dispersal, attracting the beetles into the felling area. Spatial analyses show that capture patterns were autocorrelated up to distances of about 250 m.