Current issue: 54(2)
Bark beetle populations live usually in a balance in natural forests, and outbreaks occur seldom. The populations have been found to increase in managed forests. Fellings affect the structure of the forests, which influence the living conditions of the insects, and produce material for reproduction. In this study the occurrence of bark beetles was studied in a forest area in Etelä-Häme in Southern Finland using line plot survey.
The forests in the area were Norway spruce (Picea abies L. Karst.) dominated. Over third of the 140 sample plots studied were in forests which had never been cut or it was over ten years to the last logging. Bark beetles of 26 different species were found in 66 of the sample plots. The most common species was six-toothed spruce bark beetle (Pityogenes chalcographus L.), which was due to the abundance of growth material suitable for the species in the area. New species in the area were common double-eyed spruce bark beetle (Polygraphus polygraphus L.), Pityophthorus micrographus L., and Dryocetes-beetle (either Dryocetes autographus or D. hectographus). The fellings increased the occurrence of beetles. The amount and quality of logging residue affected the abundance of the insects.
The PDF includes a summary in German.
In the winter of 1977/78, a White-backed Woodpecker (Dendrocopos leucotos Bechstein) was observed in the archipelago of southwestern Finland 200 km from its breeding areas. It foraged on insects living in mall dead alder and birches. The potential prey species were identified by rearing the insects from the trunks used by the White-backed Woodpecker. Altogether 628 adult insects emerged. In addition to the big larvae the potential food also included larvae of Sciaridae and Cecidomyidae (Diptera) living in dense clumps.
The writer reports in this discussion article of four stands in Finland that have died due to a bolt of lightning. A death of a group of trees because of lightning has been relatively uncommon for the forest professionals. The trees may not have no lightning marks. The four sites are presented in detail. Characteristic for this type of death of trees is, for instance, that trees have died within a circular area (of usually 30 m of diameter), only conifers have died, trees die from the top down, sometimes marks can be found in trees in the centre of the area, and under the bark may be brown patches or stripes.
A survey was conducted in Finland in 1988 to determine whether the pine wood nematode Bursaphelenchus mucronatus Mamiya & Enda 1979 (Nematoda: Aphelenchoididae) or the closely related species B. mucronatus would occur in Finnish forests. Dead or dying standing trees and timber of two conicer species, Pinus sylvestris L. (Scots pine) and Picea abies (L.) H. Karst. (Norway spruce) were analysed for the presence of these nematodes. Monochamus spp. pine sawyers (Coleoptera: Cerambycidae) were also collected and inspected for the presence of dispersal fourth juvenile stages (dauerlarva) of the nematodes. The species B. xylophilus was not found, but B. mucronatus appeared to be widespread in the country. Individuals of this nematode were found both from Scots pine and Norway spruce. Adults of two Monochamus species were found, M. galloprovincialis and M. sutor. Only two of the examined beetles of the former species had dauerlarvae in their body.
The PDF includes an abstract in Finnish.
In a locality in Southern Finland where the white-backed woodpecker, Dendrocopos leucotos (Bechst.), was previously breeding was found many conical borings excavated during the winter in young aspens (Populus tremula L.) on average 8.1 cm in diameter. Full-grown larvae of Saperda carcharias (L.) (Coleoptera, Cerambycidae) hibernated in pupal chambers constructed about 0.5 m above ground level. Below this chamber the larva has usually prepared an exit hole. After the larva has blocked itself in the pupating chamber it is easy to prey for the woodpecker during the whole winter.
There were usually 1–5 conical borings in the same trunk. The number of these borings did not correspond with the amounts of larvae eaten, since the woodpecker often made these borings in places from which it could not obtain a prey. The woodpeckers stopped excavating in those cases when the larvae in the galleries were dead. The exit holes and the conical borings occluded within a few years. The galleries within the tree will not heal and several years later a new larva may utilize them. In the wintering habitats of the white-backed woodpecker the availability of food could be improved by increasing the amount of S. sarcharias larvae. This is easily done by encouraging young aspens.
The PDF includes a summary in Finnish.
The dying-off of more trees in an over-aged Norway spruce (Picea abies (L.) H. Karst.) stand caused by Ips-bark beetles was reduced by a pheromone preparation, ipslure. 20 preparations placed in trapping bolts captured more than 13,700 specimens of Ips typographus L. and Ips duplicatus Sahlb., which alone corresponded to a saving of five old trees in this valuable exhibition and seed collection stand. Attractance of ipslure to the following predators of bark beetles was also examined; Thanasimus formicarius, T. rufipes, Epuracea bickhardti, Rhizophagus ferrugineus, Pityophagus ferrugineus.
The PDF includes a summary in English.
The paper deals with the problems of the preservation of the redwood groves (Sequioia sempervirens (D. Don) Endl. and Sequoiadendron giganteum (Lindl.) J. Buchholz) in California. The activity to protect these groves from flood and fire may finally lead to dying of these long-lived trees. A program to use prescribed burning as a tool for the management of natural ecosystem has been started.
The PDF includes a summary in English.
Experimental applications of the nuclear polyhedrosis virus (Borrelinavirus diprionis) to control of the European pine sawfly (Neodiprion sertifer Geoff.) was carried out during the last outbreak of this sawfly in in Scots pine (Pinus sylvestris L.) in Finland in 1963. Quantities of polyhedrosis virus preparation, collected and purified in Finland were available as concentrations packed in capsules. Spraying took place in three localities in southwestern Finland when the larvae were in I–III instars.
When Finnish and Swedish preparations were used 83–96% of larval colonies were completely destroyed within 14 days. In addition, an attempt was made to change the virus in latent stage, present already in the area, to acute stage by application of substrates which are probably harmless to pine, but were expected to stress the larvae. Ground quarts as spray had the best lethal effect upon larvae.
The PDF includes a summary in English.
Degree of decomposition of logging residue, and decay in stumps have been used in forest inventories to estimate the time of the felling. In this paper, a method was developed to use insects breeding in the logging residue to determine how long ago the felling took place. The method is based on the arrival and rate of development of the different species of bark beetles that breed in the logging residue.
The most suitable insect species to be used in the purpose of timing the age of logging residue were defined, and their occurrence in different tree species and fellings performed at different times of the year were described. The species can be easily identified by gallery systems characteristic to the species.
It is concluded that the method does not suit for broadleaved species, because there is no common insects suitable for this purpose. Also, the time of swarming of the insects depends on the weather conditions in the spring, which makes it difficult to give definite dateshe progress of the spring has to be taken into account when the occurrence of the insects is used in the determination of the time of the felling. In addition, local conditions, such as shading, affect drying of the branches, and can influence the occurrence of the insects. For Scots pine and Norway spruce the age of the logging residue can be determined precisely only at most two years back.
The article presents the studies about antagonistic influence of insect pathogenic fungi Beauveria bassiana (Bals.) Vuill. and B. tenella (Delacr.) Siem. against root rot diseases. The experiments were conducted in laboratory where the fungi were grown in Petri dishes. The results show that these fungi are antagonistic with each other. The used stem of B. bassiana was proved as strongest antagonist against all studied F.annosus.
The PDF contains a summary in German.