Semiochemicals and the integrated management of Ips typographus (L.) (Col., Scolytidae) in Belgium.
A research project was set up in Belgium to investigate the possibility of using poisoned trap-trees for protecting timber or live stands of Picea against scolytid pests. Several pyrethroids with sufficient persistence were provisionally selected for use against Ips typographus and Trypodendron lineatum. Lying and standing trap trees (insecticide-treated and bearing a pheromone dispenser) were tested, particularly against I. typographus. The spatial distribution of insects which landed around the pheromone dispensers and were subsequently killed was analysed and the total numbers caught were estimated. The results showed that trap trees attract 2-14 times as many I. typographus as traps. To establish a measure of the impact of trap trees on scolytids, the size of overwintering I. typographus populations was estimated by sampling both the bark of trees attacked in late summer of 1990 and the litter around these trees. In June-July, each trap tree caught on average slightly less than the overwintering population from 1 tree attacked in late 1990. Guidelines for trap tree establishment could probably be derived from these assessments. An analysis of the impact of trap trees on natural enemies showed that the numbers of parasites and predators represented 2.5% of the number of I. typographus caught.