Semiochemicals and the integrated management of Ips typographus (L.) (Col. Scolytidae) in Belgium

Until recently, the management of spruce bark beetles in Belgium has relied upon felling, debarking and removal of susceptible or infested material, and in a number of cases, on the use of pheromone traps. Gradually, due to the cost of manpower, on-site debarking has been replaced by lindane spraying. Experimental work to design new management techniques was started in 1989, when plans were developed by the Regional Government of Wallonie to ban lindane from the forest. Later on, in February 1990, severe storms causing 2.6 millions cubic meters of spruce windfalls considerably increased the need for improved control methods. As a result, a co-operative research project was setup to investigate the possibility of using poisoned trap-trees for protecting timber or live stands. To date, several pyrethroids with sufficient remanence have been provisonally selected for use against Ips typographus and Trypodendron lineatum. Lying and standing trap trees (insecticide-treated and bearing a pheromone dispenser) have been tested, particularly against I. typographus. The spatial distribution of insects landing around the pheromone dispensers and subsequently killed was analysed and hence, the total numbers caught were estimated. These results were compared to the catches of artificial traps, showing that trap trees catch 2–14 times as many I. typographus as traps. To establish a measure of the impact of trap trees on bark beetles, the size of overwintering I. typographus populations was estimated by sampling both the bark of trees attacked late in the summer 1990, and the litter around these trees. In June-July, each trap tree caught on average slightly less than the overwintering population from one tree attacked in late 1990. Guidelines for trap tree establishment could probably be derived from these assessments. Trap tree impact on natural enemies has been analysed in one site. Numbers of parasites and predators represented 2.5% of the number of I. typographus caught. Presently, removal of infested material and trap tree deployment are standard methods used by the Regional Forest Service in Wallonie.FLWNA