Monitoring of Ips typographus and Pityogenes chalcographus: influence of trapping site and surrounding landscape on catches

1 The influence of trapping site (i.e. fresh clear-cuts) characteristics and habitat amount (i.e. area of stands that may hold breeding material) in the surrounding landscape on catches of the bark beetles Ips typographus (L.) and Pityogenes chalcographus (L.) in pheromone-baited flight-barrier monitoring traps was studied. 2 For the two species, the study investigated: (i) the extent of the variation in catches among trapping sites; (ii) the extent of this variation that can be explained by models including trapping site characteristics (clear-cut size, percentage of spruce in the cut stand, altitude) and habitat amounts in the surrounding landscape; and (iii) the spatial scale at which beetles respond to the habitat amount in the landscape. 3 The variation in catches among trap sites was 15-fold larger for I. typographus than for P. chalcographus. There was a positive relationship between the catches of I. typographus and (i) the percentage of the surrounding landscape covered by mature spruce forest at radii 5004000 m and (ii) the percentage of spruce in stands cut when the clear-cuts used as trapping sites were created. For P. chalcographus, only the second relationship could be demonstrated. 4 Thus, for monitoring of I. typographus: (i) several trapping sites per landscape are required; (ii) the amount of mature spruce forest around trapping sites needs to be considered when choosing trapping sites; and (iii) the trapping sites need to be standardized with respect to the percentage of spruce in the cut stand when fresh clear-cuts are used. For P. chalcographus, fewer trapping sites per landscape are required and only the percentage of spruce in the cut stand needs to be considered.