Browsing by Subject "Ips typographus"

The European spruce bark beetle (Ips typographus L.) is one of the most concerning forest pest to Norway spruce (Picea abies Karst) forests in Central and Northern Europe. The species has been fairly well studied, especially after the storm Gudrun in Sweden in 2005 and some widespread damages in spruce forests in Central Europe in the recent years. I. typographus is a highly opportunistic species and a population can expand drastically if favorable conditions, mainly weakened or windthrown trees and suitable temperatures, are met. After reproducing on these favorable conditions, the species may have reached a population size so large that it is capable of infesting and killing even standing, healthy trees in the nearby areas. Damages caused to standing trees are the most problematic as there losses in economic revenue, carbon storage and, in some cases, ecosystem services. In Finland, the problems caused by I. typographus have fortunately been localized, but with climate change increasing extreme weather patterns, the problems are likely to increase in the future, which is why the species, as well as other potentially problematic species should be studied as intensively as possible, so that informed decisions can be made in case of a windthrown or other pest inducing event was to occur. After the Asta-storm in 2010, some 9000 cubic meters of wood had fallen in Ruokolahti municipality. Quickly after the storm, two areas (Viitalampi and Paajasensalo) were conserved under METSO-program and no commercial harvests were done in the sites, and permissions for bark beetle studies were given to increase knowledge especially on I. typographus. The two sites were mostly harvest-ready or mature Norway spruce dominated forests. Field work began in 2011 in Viitalampi, and new study plots were established in Viitalampi and Paajasensalo in subsequent years. To study bark beetle population dynamics, a total of 140 fallen trees were studied. From each tree diameters were measured at base (d0), breast-height (d1.3) and ten meters (d10), as well as full height of the tree. An entomological analysis was done in two-meter intervals (from 0m to 10m) to establish changes of bark beetle activity on a stem. A 25cmx50cm piece of bark was analyzed on each height, from which new and old entry and exit holes and different bark beetle maternal galleries were calculated. This was done on a different tree each year on a plot, although it was done only to trees which had root connections to the soil and were thus deemed alive and potential breeding and feeding ground for bark beetles. In addition, National Land Survey of Finland provided high resolution aerial images from the study sites so that the surrounding areas and conditions could be taken into account in studying bark beetle population dynamics. From the aerial images, a number of fallen and standing trees were calculated on a 25-meter zone around the center of a plot, as well as the size of the closest windthrown gap and the plot’s distance to that gap. The analysis of each measured factors’ significance to I. typographus maternal gallery density (m²) were calculated with Generalized Linear Models. Yearly changes in I. typographus occurrence were expectedly high and complied with observations in previous studies. In addition, there was a significance found in gap size and distance to gap in 2013, which could be explained with population behavior in previous years and with the exhaustion of larger and more nearby resources in the beginning of population build-up. Extensive field work combined with aerial images and other spatial tools are important in understanding the complexity of bark beetle, or any other forest pest, population dynamics. As extreme weather patterns increase, so do the damages caused by biotic agents, such as the European spruce bark beetle. Future studies are needed to educate and prepare forest owners for forest disturbances, be it from the viewpoint of commercial forestry, carbon storage or biodiversity conservation.

Urban forests of Helsinki city are managed in multiple ways and several forest values are taken into account in forest management. Strong forest management actions that change the forest landscape radically have been done quite seldom, which has increased the proportion of old forests. The risk of spruce bark beetle (Ips typographus) outbreaks is often evident especially in older Norway spruce (Picea abies) forests of low vitality. In the winter of 2011 to 2012 storms caused windfalls in some areas of the urban forests in Helsinki city, which increased the risk of spruce bark beetle outbreaks even more. The objective of this study was to assessment the risk of spruce bark beetle outbreaks in the urban forest of Helsinki city and present future forest management recommendations to control the spruce bark beetle damage. Monitoring with pheromone baited traps was used as the main investigation method. Results were compared with spruce bark beetle risk estimates found in literature. Other factors affecting the risk of spruce bark beetle, for example the amount of living Norway spruces infested with the spruce bark beetle, were observed as well. Monitoring with pheromone traps was carried out with 36 traps in three regions in Helsinki Central Park and in one region in Herttoniemi between 6th of May and 4th of July in 2013. Pheromone trap model, WitaTrap Multi Funnel, and pheromone bait Ipsowit® Standard were manufactured by Witasek company. Altogether 79 210 spruce bark beetles were trapped. According to the monitoring results the risk of spruce bark beetle can be high in one region in Central Park area. Living Norway spruces infested by the spruce bark beetle were found in two regions and also in one area outside the investigation area. Based on the results the areas with greatest risk to spruce bark beetle damage were the neighboring areas of previous damage as well as forests with suitable breeding material for the spruce bark beetle. The risk can also be high in Norway spruce forests of low vitality and in recently formed, sun-exposed forest edges dominated by Norway spruce. Forest management recommendations in short time interval to control the spruce bark beetle risk are as follows 1) forest monitoring and removal of spruce bark beetle infested live Norway spruces before Midsummer, 2) observation of storm damage and removal of large diameter Norway spruce windfalls as a rule, 3) monitoring the weather conditions and 4) following national announcements related to the spruce bark beetle risk status. Forest management recommendations for longer time interval are phased regeneration fellings of risk prone Norway spruce forests and changing the forest structures more resistant to spruce bark beetle damage in the future.

The European spruce bark beetle Ips typographus (L.) is a severe pest of the Norway spruce Picea abies (Karst.). The species usually attacks weakened trees, but in a consequence of a strong abiotic disturbance event, population may increase sufficiently to threaten even healthy trees. In addition to available trees for feeding and reproduction, temperature is the most important factor limiting the damage of the pest. Limiting potential of the pest’s enemies is potentially important but poorly known. There are several predator and parasite species limiting the success of I. typographus. These species are commonly known as natural enemies or natural enemy complex. Occurrences of these species are investigated in this study. Regardless of intensive studies about natural enemies, there are still remarkable gaps in knowledge. While natural enemies could theoretically be used to control pest populations, practical applications in forestry are in a very limited use. Mechanical methods, mainly sanitation and salvation loggings, are instead used to prevent outbreaks from escalating. These management practices prevent outbreak from spreading, although damage caused by loggings may also harm trees and expose these to pathogens. Possibility of using natural enemies as a part of pest control in forestry is considered in this study. Field study was conducted in SE Finland. I. typographus and natural enemy complex were sampled in 2018 by means of trapping logs settled with fixed number of I. typographus individuals. This was conducted in three different stand classes representing different gradation phases in forests to find differences between regulating potential of enemies. Stand classes were chosen based on the visible symptoms of bark beetle infestation and disturbance history. Classes were healthy (no attack), early outbreak (first symptoms and increased pest population) and declined outbreak (earlier outbreak, pest already declined near endemic level). Trapping logs with settled I. typographus were allocated to these classes, and insects emerging from trapping logs were later collected for sampling in sealed funnel traps. I. typographus population level was simultaneously monitored using pheromone traps. Differences between insect occurrences in different stand classes were statistically analysed by Kruskal-Wallis test with 0.05-level of significance for each identified enemy species and families. Spearman correlation was also used to detect any possible relations between different enemy species. Predators emerging from the logs were identified to six coleopteran families. Species were Thanasimus formicarius (Cleridae), Plegaderus vulneratus (Histeridae), Epuraea spp. (Nitidulidae), Rhizophagus spp. (Monotomidae) and from Staphylinidae Quedius plagiatus, Nudobius lentus, Phloeonomus spp., Leptusa spp. and Placusa spp. Family Elateridae was inspected as a single tested group. Predatory flies and parasitic wasps also emerged from the logs, although these were excluded from the current study. Three species had significant preference to certain outbreak classes. P. vulneratus proved most promising regulator in this study. It reproduced rapidly already during the first year of infestation. T. formicarius had significant preference for stand class, but failed to occur in sufficient numbers during the first year of infestation to have impact on the I. typographus population. Staphylids Phloeonomus spp. were very common at all stand classes but preferred healthy class. For both P. vulneratus and Phloeonomus spp. preferences for stand classes were significant, but the regulation effectiveness of these species is relatively unknown. Results suggested that limited resources in the healthy class, similar to managed forests forces both bark beetles and predators into same space, potentially increasing mortality. This result was observed by increased total numbers of beetles in the trapping logs of healthy class in comparison to outbreak classes, while simultaneously prey-predator ratio was also lower. This means that in addition to removing resources, sanitation loggings could also have increasing effect on enemy induced mortality. Small amount of deadwood potentially sustains higher endemic population of enemies, potentially increasing stands resistance to further insect induced disturbances. While some enemies were more common at the declined outbreak class, this claim was not supported by this study.