Det är ingen större risk för insektsskador på omgivande granskog vid lagring av skogsbränsle. Det... more Det är ingen större risk för insektsskador på omgivande granskog vid lagring av skogsbränsle. Det är en slutsats som kan dras av en studie i Uppland och södra Dalarna. Under tre somrar placerades högar av fällda unggranar i kanten mellan hygge och granungskog på 31 försöks- platser. På samtliga platser blev det angrepp av sex- tandad barkborre på omgivande skog,
We investigated the effects of Bacillus thuringiensis variety kurstaki x aizawai (Bt) on infestat... more We investigated the effects of Bacillus thuringiensis variety kurstaki x aizawai (Bt) on infestation levels of two lepidopteran insects as well as on seed quality in Norway spruce, Picea abies L. (Karst.) in central Sweden. Spruce flowers (female strobili) were sprayed with a 0.2% suspension (wt:wt) of the Bt preparation Turex 50 WP, 25,000 IU/mg in water. To expose even those lepidopteran larvae that feed exclusively embedded within the cone tissue, the Bt treatment was applied to open flowers, before they closed and developed into cones. The experimental design included three main factors: treatment (untreated control, water, or Bt), spruce genotype (three clones), and spraying time (spraying before, during, and after the phase of highest pollen receptivity). The Bt treatment reduced the proportion of cones infested by the cone worm Dioryctria abietella Den. et Schiff. (Lepidoptera: Pyralidae) from approximately 30 to 15%. There was no statistically significant treatment effect on...
Forest productivity is expected to increase in the future owing to the use of genetically improve... more Forest productivity is expected to increase in the future owing to the use of genetically improved plant material and climate warming. Increased productivity will lead to shorter optimum rotation lengths and larger annual clear-cut areas. This study explored the likely effects of ...
ABSTRACT Damage by the large pine weevil, Hylobius abietis (L.), is a major threat to conifer pla... more ABSTRACT Damage by the large pine weevil, Hylobius abietis (L.), is a major threat to conifer plantations throughout Eurasia, but damage is usually less severe in northern areas. However, pine weevil damage seems to increase if the sites are burnt. The aim of this study was to determine the effects of variations in the time of planting (with respect to the total age of the clear-cut and the time since burning) on pine weevil damage to seedlings on burnt sites in northern Sweden. The study also explored whether there is an optimal time for planting at which damage levels are reduced to acceptable levels. Ten sites were selected in an inland area of northern Sweden where pine weevils are normally scarce. The sites were dry–mesic and represented a range of times since clear-cutting and since burning. The sites were planted in June 1998, 1999 and 2000 with 1-year-old container-grown seedlings of Norway spruce [Picea abies (L.) Karst.]. Pine weevil damage was reduced if planting was done no earlier than 3 years after clear-cutting and no earlier than 2 years after burning. Planting too soon after burning, irrespective of the age of the clear-cut, resulted in unacceptably high damage levels.
The risk for damage associated with spruce bark beetle attacks on living trees was estimated in 1... more The risk for damage associated with spruce bark beetle attacks on living trees was estimated in 12 forest districts in the Nordic countries during three years. Pheromone‐baited traps and trees were used. Five groups of three traps were deployed annually on fresh spruce clear‐ ...
In field experiments in Sweden, the constituent 2-methyl-3-buten-2-ol of the aggregation pheromon... more In field experiments in Sweden, the constituent 2-methyl-3-buten-2-ol of the aggregation pheromone of the spruce bark bettleIps typographus (L.) was effectively replaced by 2-methyl-3-butyn-2-ol.
The availability of habitat for wood-dependent species has been greatly reduced in Fennoscandian ... more The availability of habitat for wood-dependent species has been greatly reduced in Fennoscandian boreal forests and hence the setting aside of forest land for conservation purposes is a common strategy. Here, we explore the biodiversity quality and conservation relevance of three categories of set-asides dominated by Norway spruce (nature reserves, woodland key habitats and retention patches, i.e. groups of living
Det är ingen större risk för insektsskador på omgivande granskog vid lagring av skogsbränsle. Det... more Det är ingen större risk för insektsskador på omgivande granskog vid lagring av skogsbränsle. Det är en slutsats som kan dras av en studie i Uppland och södra Dalarna. Under tre somrar placerades högar av fällda unggranar i kanten mellan hygge och granungskog på 31 försöks- platser. På samtliga platser blev det angrepp av sex- tandad barkborre på omgivande skog,
We investigated the effects of Bacillus thuringiensis variety kurstaki x aizawai (Bt) on infestat... more We investigated the effects of Bacillus thuringiensis variety kurstaki x aizawai (Bt) on infestation levels of two lepidopteran insects as well as on seed quality in Norway spruce, Picea abies L. (Karst.) in central Sweden. Spruce flowers (female strobili) were sprayed with a 0.2% suspension (wt:wt) of the Bt preparation Turex 50 WP, 25,000 IU/mg in water. To expose even those lepidopteran larvae that feed exclusively embedded within the cone tissue, the Bt treatment was applied to open flowers, before they closed and developed into cones. The experimental design included three main factors: treatment (untreated control, water, or Bt), spruce genotype (three clones), and spraying time (spraying before, during, and after the phase of highest pollen receptivity). The Bt treatment reduced the proportion of cones infested by the cone worm Dioryctria abietella Den. et Schiff. (Lepidoptera: Pyralidae) from approximately 30 to 15%. There was no statistically significant treatment effect on...
Forest productivity is expected to increase in the future owing to the use of genetically improve... more Forest productivity is expected to increase in the future owing to the use of genetically improved plant material and climate warming. Increased productivity will lead to shorter optimum rotation lengths and larger annual clear-cut areas. This study explored the likely effects of ...
ABSTRACT Damage by the large pine weevil, Hylobius abietis (L.), is a major threat to conifer pla... more ABSTRACT Damage by the large pine weevil, Hylobius abietis (L.), is a major threat to conifer plantations throughout Eurasia, but damage is usually less severe in northern areas. However, pine weevil damage seems to increase if the sites are burnt. The aim of this study was to determine the effects of variations in the time of planting (with respect to the total age of the clear-cut and the time since burning) on pine weevil damage to seedlings on burnt sites in northern Sweden. The study also explored whether there is an optimal time for planting at which damage levels are reduced to acceptable levels. Ten sites were selected in an inland area of northern Sweden where pine weevils are normally scarce. The sites were dry–mesic and represented a range of times since clear-cutting and since burning. The sites were planted in June 1998, 1999 and 2000 with 1-year-old container-grown seedlings of Norway spruce [Picea abies (L.) Karst.]. Pine weevil damage was reduced if planting was done no earlier than 3 years after clear-cutting and no earlier than 2 years after burning. Planting too soon after burning, irrespective of the age of the clear-cut, resulted in unacceptably high damage levels.
The risk for damage associated with spruce bark beetle attacks on living trees was estimated in 1... more The risk for damage associated with spruce bark beetle attacks on living trees was estimated in 12 forest districts in the Nordic countries during three years. Pheromone‐baited traps and trees were used. Five groups of three traps were deployed annually on fresh spruce clear‐ ...
In field experiments in Sweden, the constituent 2-methyl-3-buten-2-ol of the aggregation pheromon... more In field experiments in Sweden, the constituent 2-methyl-3-buten-2-ol of the aggregation pheromone of the spruce bark bettleIps typographus (L.) was effectively replaced by 2-methyl-3-butyn-2-ol.
The availability of habitat for wood-dependent species has been greatly reduced in Fennoscandian ... more The availability of habitat for wood-dependent species has been greatly reduced in Fennoscandian boreal forests and hence the setting aside of forest land for conservation purposes is a common strategy. Here, we explore the biodiversity quality and conservation relevance of three categories of set-asides dominated by Norway spruce (nature reserves, woodland key habitats and retention patches, i.e. groups of living
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Papers by Jan-olov Weslien