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We investigated the wood fungal community composition in stems of living Norway spruce (Picea abies (L.) Karst.) trees in 20–40 year-old forest stands from Latvia that differed in recent management history (stands with or without thinning) and former land use (former agricultural or former forest lands). Fungal internal transcribed spacer (ITS2) amplicons of DNA extracted from wood were sequenced to assess wood fungal communities. Alternaria, Ascocoryne, Didymella, Heterobasidion, Ophiostoma, Orbilia, Pesotum, Phoma and Pseudocercosporella were the dominant wood pathogen and wood saprotroph genera in the analysed samples. PERMANOVA analysis identified some differences in fungal communities among site types analysed (p < 0.001); tree height and presence/absence of rot in the wood samples (mainly Heterobasidion rot) significantly influenced fungal community composition (p < 0.001). Significant negative co-occurrence (p < 0.05) was observed between Heterobasidion and Ascocoryne genera indicating the differing wood colonizing niches of these taxa. Both stand level factors, such as management history and former land use, and tree level parameters are significant for wood inhabiting fungal communities of living spruces. [ABSTRACT FROM AUTHOR]

Heterobasidion parviporum and H. annosum are the most damaging root and butt rot pathogens of conifers in southern Fennoscandia where their distribution and frequency are reasonably well described in literature. However, in the most northern boreal forests of Europe the occurrence and significance of these pathogens is poorly known. In the future global warming may increase root and butt rot damages in the North. In this research the distribution of Heterobasidion spp. in northern Finland was compiled from literature and various available databases and from a field study in two counties of northern Finland, Northern Ostrobothnia and Kainuu. Conifer stumps from 101 regeneration cutting sites were inspected and sample discs from stumps with signs of decay were investigated for the presence of Heterobasidion spp. In all, 11,846 stumps were investigated. Decay was found in 429 Norway spruce stumps and 50 Scots pine stumps. H. parviporum was isolated from five spruce discs, each from a different site. H. annosum was not detected. According to previous records H. annosum has been identified only twice in northern Finland and these locations are over 600 km south of the northernmost Scots pine stands in Fennoscandia. Instead, H. parviporum occurs sporadically in the whole distribution area of Norway spruce in northern Finland. Most probably H. parviporum can be found in overmature dense stands at fertile sites but even there only at low frequencies. In northern Finland butt rot of conifers is caused mainly by other decay fungi than Heterobasidion . Low pH of the organic soil layer is probably a significant factor hampering H. parviporum from spreading in the North. [ABSTRACT FROM AUTHOR]

Heterobasidion butt rot causes considerable losses to forestry in coniferous forests in many parts of Europe including southern Fennoscandia. In northern Fennoscandia, including central and northern Finland, both Heterobasidion annosum and H. parviporum are rare. This study aimed to determine the incidence of butt rot in Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies (L.) Karst.) north of the area commonly infested by Heterobasidion spp. in Finland. The incidence of butt rot in these conifers was investigated in Northern Ostrobothnia and Kainuu using two data sets: stump inspections in 101 regeneration cutting sites and the Finnish National Forest Inventory (NFI) data. According to stump inspections butt rot occurred in 1% of Scots pine trees and 10% of Norway spruce trees. In the most recent NFI data from 2009 to 2011 the incidence of trees with rot in mature managed stands of these two counties was 1% and 5% for Scots pine and Norway spruce, respectively. According to NFI, these values are nearly equal to the average incidence of butt rot in mature pines and spruces of the whole of Finland. Consequently, the low incidence of Heterobasidion butt rot in these parts of Finland does not mean lower occurrence of butt rot. Butt rot incidence varied greatly between sites: 0–24% of Norway spruce stumps in spruce dominated sites and 0–13% of Scots pine stumps in pine dominated sites were infected. High butt rot incidence in Norway spruce was associated with high site fertility, stand age, low organic matter content of soil and low temperature sum of the site. In Scots pine butt rot appeared after stand age exceeded 120 years while decay occurred already in 40–80 years old Norway spruces. High butt rot incidence in Scots pine was associated also with high flow accumulation of the site. Precipitation, plot slope, plot aspect, ditches, stand density and elevation were insignificant variables in models explaining decay incidence. During 1991–2013 butt rot incidence in Scots pine or Norway spruce has not changed in the study area. Similarly, to the more southern areas with high Heterobasidion risk, butt rot control in the North should focus especially on fertile mineral soil sites. [ABSTRACT FROM AUTHOR]

The goal of this study was to assess the long-term effects of partial harvesting and supplementary soil scarification on the frequency of root and butt rot in managed uneven-sized Norway spruce stands. Frequency of rot and the population structure of the rot fungi were assessed on 1353 stumps after clear-cutting 21 years after a selection harvesting experiment. The initial experiment was comprised of three harvest strength (low, intermediate and high) of single-tree selection, removing approximately 25, 45 and 65% of the stand basal area. Uncut control plots were established at the same time. Supplementary soil scarification was applied in subplots within the single-tree selection plots, using a medium-sized excavator. After clear-cutting the stumps were analyzed with respect to rot caused by Heterobasidion parviporum , Armillaria spp., Stereum sanguinolentum as well as other rot fungi. Rot caused by Armillaria spp. was most common (8.6% of the stumps), while infection by H. parviporum (2.9%) or S. sanguinolentum (3.0%) was less frequent. The group “other rot” (5.4%) comprised 21 identified taxa, each occurring in 1–15 stumps. Significantly lower rot frequencies were found for the uncut control (16.3%) and intermediate harvest strength (15.7%), compared with low harvest strength (23.6%). A rot frequency of 21.0% was found in the high harvest strength. In two of three harvest strengths, the rot frequency was higher than for the uncut control. As the observed rot frequencies did not increase consistently with increasing harvest strength, the results do not completely support the initial expectations of increased rot after single-tree selection compared with the uncut control. However, since the probability of rot in individual stumps on plots treated with single-tree selection was significantly affected by the distance to the nearest strip road ( H. parviporum ) as well as dependent on the size of and distance to the nearest stump of trees cut during the experimental harvest ( H. parviporum , S. sanguinolentum and total rot), it is evident that the single-tree selection harvesting was partially responsible for some of the observed rot. One of the selection criteria in the initial harvest was a sanitary removal of trees of poor vitality. Varying degrees of sanitation felling may therefore have offset the effects of new infections in wounds or spread of rot fungi through adjacent stumps. Supplementary soil scarification in small gaps of the residual stand had no significant effect on the frequency of rot, suggesting that such treatment may be used to facilitate regeneration in uneven-sized spruce stands on similar sites. [ABSTRACT FROM AUTHOR]

Protection against the root rot fungus Heterobasidion annosum s. l. is achieved by mechanically spraying stumps with spores of the antagonistic fungus Phlebiopsis gigantea , commercialized as Rotstop® . An extensive colonisation of the stump by P. gigantea is required for protection. Colonisation may depend on how the biocontrol agent interacts with the fungal community that is endophytically inhabiting the stump, as well as with other fungi establishing after the treatment is applied. In this research, we studied how the distribution and abundance of Heterobasidion and P. gigantea is modulated by the fungal community inhabiting Norway spruce ( Picea abies ) stumps. First thinning stumps were treated with Rotstop and/or artificially inoculated with H. parviporum under field conditions. After two months, P. gigantea or Heterobasidion distribution was measured by qPCR, and both pathogen and biocontrol abundance gradients were correlated with members of the fungal community determined by high throughput sequencing. Rotstop application decreased Heterobasidion biomass by almost 200 times, though the strongest biomass reductions were only achieved when stumps were well covered by P. gigantea . Poor Rotstop applications resulting in, for instance, a drop of 20% in terms of stump covered area by the biocontrol, were associated with a 2-fold biomass increase of the surviving Heterobasidion colonies. Unlike Heterobasidion , some fungi such as Peniophora sp. and F. pinicola did not change their relative abundance following the Rotstop treatment and were associated with areas of low P. gigantea presence. Yeast-like fungi of the genus Debaryomyces increased its relative abundance following Rotstop treatment, and were the only taxa associated with both a higher abundance of the biocontrol, and a lower abundance of the pathogen. Ours is the first study quantifying at microscale the interaction between H. parviporum and P. gigantea in stumps subjected to Rotstop treatment, showing how incomplete stump cover may result in large shifts in terms of biomass for either the pathogen or the biocontrol. Our results stress the importance of achieving a complete cover of the stump surface in practice. Debaryomyces sp. might facilitate P. gigantea colonisation of the stump and could be added as enhancers of Rotstop treatment, though the mechanism of interaction with the pathogen and the biocontrol should be further studied. [ABSTRACT FROM AUTHOR]

The Heterobasidion annosum species complex is a widely distributed group of fungal conifer pathogens causing root and butt rots. We studied the key processes of Heterobasidion epidemiology by compiling models that rely on biological processes. Models were included in the mechanistic model with stochastic elements, Hmodel, simulating the fungal dynamics in even-aged Norway spruce stands. The results from the modelling and stand-level simulations indicated that primary infections are affected by the stump size and spore deposition. In addition, we found that Heterobasidion dynamics at the scale of the stand are driven by several infections in large stumps, rather than by numerous infections in small stumps. We assessed the need for quantitative results in Heterobasidion biology, especially in the spread mechanisms, to support the development of complex mechanistic models. [ABSTRACT FROM AUTHOR]

In boreal forests, stumps of Norway spruce are removed after clear cutting to gather wood for energy and, additionally, to reduce damage caused by the root rot fungus, Heterobasidion parviporum . In order to understand the behavior of H. parviporum at stump-harvested Norway spruce sites, the survival of Heterobasidion mycelia in buried root fragments and their ability to infect nearby spruce seedlings was investigated in southern Finland. The longevity of Heterobasidion mycelium in investigated root pieces exceeded the follow-up period of 83 months. After six years, 18% of the root fragments yielded living Heterobasidion mycelia. The survival of H. parviporum in root fragments was highest in sandy soils and increased with increasing volume of root fragment. The probability of occurrence of the fungus was highest when at least 60% of the root volume was originally colonized by the fungus, irrespective of the state of decay. It took 4.5 years until roots of the first seedling reached the buried root fragment and the seedling became infected by H. parviporum mycelia. After six years, 8% of the seedlings were found to be infected. In addition, the number of root residuals, i.e., the potential infection sources of the next tree generation, was determined at five stump-harvested Norway spruce sites. At these slightly infested spruce sites, on average 1500 potential disease sources ha −1 (in the form of decayed root fragments ⩾ 1.5 cm in diameter) were found in the upper soil layer after stump removal. Thus, our results indicate that stump harvesting procedure aimed at gathering wood for energy may not be an efficient way to remove infected wood material from forest soils. Furthermore, our survey on stored stumps next to clear-cut areas showed that the formation of Heterobasidion fruiting bodies may be abundant in decayed stumps in the lowest parts of the storage pile. In order to avoid increased risks of spore infection in nearby forests, decayed spruce stumps, including the lowest muddy stumps, should be transported within two years from forest storage to the end-user. [ABSTRACT FROM AUTHOR]

The southeastern United States is among the most productive forested areas in the world. Four endemic southern pine species – loblolly, longleaf, shortleaf, and slash – contribute significantly to the economic and ecological values in the region. A recently described phenomenon known as Southern Pine Decline (SPD) has been reported as having widespread impact in the southern pine region, particularly on loblolly pine. Root-feeding weevils and their associated fungi have been suggested as causal agents, even though literature and empirical research suggests that they are secondary insects colonizing weakened trees. Further, no published information exists about whether their associated fungi can cause mortality of mature trees in the southeastern U.S. Since there are significant management implications for pine health, we reviewed and critically examined the SPD phenomena on the southern landscape. Our regional analyses of USDA Forest Inventory and Analysis data show no discernable patterns related to pine growth or mortality, especially as related to topographic factors. There are no large-scale patterns related to pine mortality suggesting multiple interacting factors impacting tree health at stand-level. As such, the hypothesis that SPD is a regionally important decline syndrome and labeling declining southern pine stands as SPD is not supported. Instead, we discuss many abiotic (soil types, climate) and biotic (insects, pathogens, genetics) factors that may be interacting with each other and affecting southern pine health. Finally, we suggest management recommendations for landowners with pine health issues. [ABSTRACT FROM AUTHOR]

Scots pine sawdust, composted bark or coarse, post-harvest woody debris from conifers had been spread over the surface of barren forest soil before planting with Scots pine. The effects of the Scots pine sawdust, composted bark or coarse, post-harvest woody debris from conifers on the abundance and diversity of culturable fungi were investigated. The amendments were aimed at increasing the soil suppressiveness to Armillaria and Heterobasidion. The classical soil-dilution method was chosen for qualitative and quantitative analyses of fungal communities in soils because of its proven reliability and consistency. The soil was inhabited by saprotrophic fungi from Ascomycota and Zygomycota, including species known to be potential antagonists of Armillaria or H. annosum (i.e. Clonostachys + Trichoderma spp., Penicillium commune, P. daleae, P. janczewskii) or stimulants of Armillaria (i.e. Pseudogymnoascus roseus, Trichocladium opacum). Eleven years after treatment, the abundance and diversity of fungi, the abundance of P. commune, and locally the abundance of P. janczewskii increased, while Clonostachys + Trichoderma spp., and locally, P. daleae and T. opacum decreased. Amending the barren soil with organic matter does not guarantee effective, long-term suppressiveness of the sandy loam soil to Armillaria and Heterobasidion. Increased abundance of entomopathogenic and nematophagous species, 11 years after treatment, does suggest the long-term possibility of insect or nematode control in soil. [ABSTRACT FROM AUTHOR]

Effects of different pre-planting soil preparations and post-harvest wood debris applications in a clear-cut Scots pine plantation, on the abundance, diversity, and activity of culturable microorganisms were investigated. The investigation was done 9 years after the re-plantings had been done. This formed part of an investigation of silvicultural practices for conservation and the biological control of Armillaria and Heterobasidion in northern temperate forests (Poland). The treatments being compared, were expected to have altered the soil's physical and chemical properties, and consequently, its biological properties. Only soft-rot microfungi from the Ascomycota and Zygomycota were detected in the soil. Fungi, including those antagonistic to Armillaria and Heterobasidion, were more abundant after shallow ploughing than after deep ploughing or ridging, and where chipped rather than coarse wood debris was left on the soil surface or incorporated. Scots pine trees had the most biomass and the least mortality after ridging and leaving coarse wood debris on the surface (associated with only a relatively moderate abundance of fungi). [ABSTRACT FROM AUTHOR]

Highlights: [•] Trees were uprooted to investigate the impact of Heterobasidion on tree growth. [•] Despite no aboveground symptoms, up to 32% of root volume was infected. [•] Aboveground tree characteristics are not reliable disease indicators. [•] Annual volume increment decreased with increasing root volume infection. [•] Stump treatment or winter thinning are recommended to minimize losses. [ABSTRACT FROM AUTHOR]

Abstract: Stump-to-tree spread is a key step in the root and butt-rot disease caused by Heterobasidion annosum sensu lato. In Norway spruce stands, Heterobasidion parviporum is more likely to spread to neighbouring trees from stumps with a large diameter than from small stumps. However, H. annosum sensu stricto does not appear to share this pattern of infection. Given that the ratio of heartwood to sapwood varies depending on the size of the stump, we investigated the role of heartwood and sapwood in stump infection by H. parviporum and H. annosum s.s. To determine whether heartwood–sapwood susceptibility was different in different host species, both Norway spruce and Scots pine stumps were included in the study. Sapwood, heartwood and the border zone between sapwood and heartwood of spruce stumps and the heartwood and sapwood of pine stumps were artificially inoculated with different genotypes of H. annosum s.s. and H. parviporum. Only one zone was inoculated per stump. Infection was assessed 2 and 10months after inoculation at 5 and 30cm below the point of inoculation. On spruce stumps, H. parviporum and H. annosum s.s. were mostly confined to the heartwood. The area infected by H. annosum s.s. was smaller than that infected by H. parviporum. Both sapwood and border infections tended to grow towards the heartwood, whereas heartwood inoculations tended to remain in the heartwood, indicating that heartwood was more favourable for H. parviporum and H. annosum s.s. colonisation in spruce stumps. On pine, heartwood colonisation failed and only H. annosum s.s. was found in the sapwood. Our results suggest a possible association between the size of the stump and the spread of H. annosum s.s. to neighbouring trees mediated by the heartwood content, suggesting that screening for heartwood resistance could be a potentially interesting direction for future research. Treating stumps at final felling would be advisable owing to the large area of heartwood exposed by this operation. [Copyright &y& Elsevier]

Abstract: The incidence of Heterobasidion spp. infections following different thinning regimes in Norway spruce was evaluated on 12 plots in a trial in southern Sweden. The plots were established in 1961 and followed until final felling in 2001. The treatments ranged from one light thinning at the experimental set-up to six thinnings. The average incidence of decay was 44% across all thinning regimes of which Heterobasidion spp. was identified in 85% of the cases. There was no difference in the incidence of infections, decayed volumes, and the size or number of Heterobasidion spp. genets among the thinning regimes. The largest genet was though found on the plot with just one light thinning and encompassed 25 trees. On average, 11.1% of the stem volume was decayed and the average height of the decay column was 4m. Decay incidence was 3.7 times the decayed volume and the height of the decay columns was 19 times the diameter of the decay at stump height. Conclusively, early thinning appears to be more important for disease development than subsequent multiple thinning. To restrict the disease development in the stand later during the rotation period, it is of utmost importance that the earlier thinnings are made during winter conditions or otherwise properly protected against spore infection of Heterobasidion. [Copyright &y& Elsevier]

Abstract: Root and butt rot from Heterobasidion parviporum on Norway spruce causes severe economic losses in northern Europe and stumps from commercial thinnings are regularly treated to prevent infection. Stumps created at precommercial thinnings are, due to their small size, believed to be unable to transfer the disease. The aims of this study were to investigate the ability of small-sized Norway spruce stumps to transfer infection to neighboring trees and to determine the lower size and age limit for disease transmission. Norway spruce trees, with diameters between 2 and 14cm at stump height, were felled at 14 sites in western Sweden. The resulting stumps were inoculated with H. parviporum and disease transfer recorded at stump height in the adjacent Norway spruce trees 5years later. Stumps covering the whole span of investigated sizes and ages could transfer infection of H. parviporum and consequently a lower limit under which transfer never occurred could not be determined. The probability of finding an inoculated infection in a tree increased with increasing diameter of both tree and stump. For a given stump size, the probability of infection in the nearby tree decreased with increasing age of the stump. It seems prudent to consider the risk of introducing H. parviporum during precommercial thinning in Norway spruce dominated stands. [Copyright &y& Elsevier]

Abstract: The making of high-stumps to benefit wood living organisms is a common practice in Scandinavian forestry. To minimise the cost of this action trees of low quality, e.g. rotten trees, are chosen if possible. In this study we investigated if the wood decay fungi Heterobasidion spp. affects saproxylic beetles assemblages in Norway spruce (Picea abies) high-stumps. In total we caught 43 species of saproxylic beetles (Coleoptera) of which one was red-listed. Associations with the fungi were tested on 13 beetle species and three of them showed negative associations with the occurrence of Heterobasidion, while none of the tested species showed a positive association with Heterobasidion. Species richness did not differ between infected (30) and non-infected (33) stumps, but the beetle assemblages differed to some extent. Two additional bracket fungi species were found on some of the high-stumps, Fomitopsis pinicola and Trichaptum spp. Both these fungi had beetle species significantly associated with them. Interestingly, we found that F. pinicola and Trichaptum spp. never occurred together in the same stumps. None of them, however, seemed to be affected by presence of Heterobasidion spp. In conclusion, Heterobasidion spp. infections influence the beetle fauna by disfavouring some beetle species but we did not find any species positively associated with Heterobasidion spp. This suggests that increasing the proportion of pre-rotten high-stumps could have a negative effect on beetle diversity on clear-cuts. [Copyright &y& Elsevier]

• On windthrown trees, more fruit bodies develop on stems compared to roots. • Uplifted roots favor the formation of fruit bodies on spruce stumps. • H. annosum produces fruit bodies on decayed spruce as frequently as H. parviporum. • Abundant fruit body formation occurs on drained peat soil. Because intensive forestry favors the spread of Heterobasidion spp., increasing amounts of decayed Norway spruce (Picea abies) wood in forest stands should be taken into account in the management of commercial forests. Spruce wood colonized by Heterobasidion spp. ensures fruit body formation, which increases the risk of new infections by basidiospores and, subsequently, the spread of Heterobasidion root rot. To date, very little is known about the prevalence of Heterobasidion fruit bodies on decayed spruce wood in different environments. To assess Heterobasidion fruit body production on various soil types and on different parts of trees, more than 36,000 fruit bodies on 425 decayed logs, 321 decayed trees, and 262 stumps of Norway spruce located on mineral and peat soils were surveyed. The most abundant fruit body formation occurred on infected spruce logs left on peat soil. Significantly more fruit bodies (average total fruit body area cm2 m−3) were found on logs on drained peat soil compared to drained mineral soil (4960 and 2674 cm2, respectively). On stems of windthrown, uprooted trees, approximately three times more actively sporulating fruit bodies were formed compared to roots. Further, approximately two times more Heterobasidion fruit bodies occurred on the roots of partly uplifted stumps than on stumps with roots remaining in the soil. H. parviporum was identified in 88% and H. annosum in 12% of analyzed spruce individuals. In cases where the tree was infected by H. annosum s.s., fruit bodies of this fungus were also commonly produced on spruce wood. Abundant development of fruit bodies was also observed in abandoned agricultural and pasture lands. Moreover, rich vegetation in fertile forest types favored fruit body development on both mineral and peat soils. On such sites, infected logs and windthrown trees, as well as partly uplifted spruce stumps, should be removed to limit the spread of Heterobasidion spp. by basidiospores. [ABSTRACT FROM AUTHOR]

• Positive effect of stump removal on the height growth of the trees was revealed. • Stump removal had no effect on the nutritional status of the needles of young trees. • Positive trend of stump removal on twig and needle parameter revealed. • Stump removal had no effect on the spread of Heterobasidion sp., Armillaria sp. • The main causal agent of root rot on all the sampling sites was H. parviporum. Stumpwood as a resource of renewable bioenergy has considerable potential in the Nordic and Baltic countries. So far, however, it has largely been left unutilised in Estonia. This study reports the results of the height growth, needle and twig traits, and Heterobasidion sp. and Armillaria sp. infection in emerging Norway spruce (Picea abies) stands after stump harvesting. After six and eight growing seasons, a significant positive effect of stump harvesting on the height growth of the trees was revealed, compared to control plots with no ground preparation. In one study site stump harvesting was revealed to have a positive effect on the morphologic parameters of twigs and needles, while no differences were noted in the other two sites. The nutrient content of the needles was similar between the treatments across all study sites. Stump harvesting had no effect on the spread of Heterobasidion sp. and Armillaria sp. in the new forest generation. Root infections in young trees with Heterobasidion sp. were detected as early as within two growing seasons from planting. The infection was most severe in the Hepatica site type stand, where 90% of the trees in the previous forest generation had been infected by Heterobasidion sp. In the two other stands studied, where the share of infected trees in the previous generation had been 26% and 16%, Heterobasidion sp. was significantly less widespread. The main causal agent of root rot on all the sampling sites was H. parviporum , but the presence of Armillaria sp. was also remarkable. [ABSTRACT FROM AUTHOR]

The article focuses on a study that shows the efficacy of two formulations including Heterobasidion and Fomes annosus in preventing colonization of red stumps. It states that the pathogen is found mainly in red pine plantations in southern Ontario and Quebec. It further mentions that Phlebiopsis gigantea used and registered as a biologicontrol agent in several European countries to demonstrate efficacy.