Monitoring spruce bark beetle (Ips typographus (L.)) populations under non-epidemic conditions
1991
Huebertz, H. (Kgl. Veterinaer- og Landbohoejskole, Koebenhavn (Denmark). Dept. of Ecology and Molecular Biology) | Larsen, J.R. | Bejer, B.
Population levels of Ips typographus in 8 Danish forest districts were monitored by pheromone traps and baited trees in 1988 and 1989. The number of trees with spontaneous colonization was also registered. All monitoring results were below earlier defined "risk thresholds", and accordingly no serious damage was found. Mean catch ranged from 3406 to 12043 beetles per trap group, and induced colonization averaged 1.08 trees per treebaiting site. The number of colonized trees (total infestation) ranged from 3.5 to 63.2 trees per 100 ha forest. Correlation was found between mean catch and induced colonization (r=0.56), and between induced colonization and total infestation (r=0.65). Accumulated data from 1988-89 and 1984-86 showed good correlation between catch size and number of infested standing trees (r=0.91). From 1988 to 1989 no significant changes occured, apart from a shift in host material from standing trees to windfalls and timber. I. typographus monitoring on regional levels is possible also under non-epidemic conditions. With a limited number of monitoring units, trapping, tree-baiting and registrations of infestation in exposed edges can give estimates sufficiently accurate to be of practical use to local foresters.
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