Using an extensive dataset from the Canton Berne spatial patterns were analysed of the first Ips typographus-infestations of standing trees after the storm Lothar on December 1999. Our results suggest that these first infestations were not caused by bark beetles indiscriminately spreading out of windthrow areas. Rather, we found relationships between levels of attacked standing trees and cleaned, scattered windthrown trees. We therefore conclude that our results point to reduced host tree resistance as a key factor.