Search

Treatment of freshly cut stumps with biological control agents containing Phlebiopsis gigantea spores effectively restricts the spread of new Heterobasidion infections in conifer forests. To test the control efficacy of different P. gigantea strains, conifer stumps or billets cut from tree stems can be artificially infected with asexual Heterobasidion conidiospores or sexual basidiospores or left for natural basidiospore infection. Currently, no information is available about whether the control efficiency of P. gigantea in Norway spruce wood is affected by Heterobasidion spore type. In the present study, the impact of four P. gigantea strains (including the commercial product Rotstop®) on initiation and development of Heterobasidion basidiospore and conidiospore infections as well as the relationship between the area occupied by P. gigantea and control efficacy were analysed in spruce billets. The mean size of the area occupied by P. gigantea was larger, and the efficacy of P. gigantea against Heterobasidion was significantly higher in billets left for natural basidiospore infection compared to treatment with Heterobasidion conidiospore suspension. The control efficacy against Heterobasidion infection was high, although only a small area of the billet surface was occupied by P. gigantea and even when there was no visible discoloration caused by P. gigantea infection on wood surfaces.

This study investigated the origins and spread patterns of Heterobasidion root disease in three Pinus contorta Dougl. ex Loudon plantations established on forest and agricultural land and subjected to three different management scenarios. Trees with decline symptoms and stumps remaining from the previous rotation were sampled for fungal isolations. Ten isolates of Heterobasidion parviporum Niemela & Korhonen and 425 of Heterobasidion annosum (Fr.) Bref. were tested for clonality through somatic compatibility tests. The following conclusions were reached: (i) P. contorta is highly susceptible to H. annosum and H. parviporum and both pathogens cause dieback of P. contorta; (ii) H. annosum from previous-rotation P. sylvestris stumps can effectively transfer to P. contorta; (iii) the pathogens may form constantly expanding territorial clones; (iv) basidiospores of both pathogens colonise stumps of P. contorta (primary infections); (v) H. parviporum clones expanded more slowly than clones of H. annosum; (vi) clonal spread proceeded more quickly from stumps with established secondary infections than from stumps with primary infections; (vii) H. annosum can persist in pine stumps for at least 26 years; and (viii) stump treatment should be considered to control Heterobasidion primary infections. Key words: lodgepole pine, Heterobasidion, primary infection, secondary infection. Cette etude porte sur l'origine et les patrons de dispersion de la maladie de racines causee par Heterobasidion dans trois plantations de Pinus contorta Dougl. ex Loudon etablies sur des terrains forestiers et agricoles et soumises a trois scenarios d'amenagement differents. Les arbres montrant des symptomes de deperissement et les souches restantes de la rotation precedente ont ete echantillonnes pour la presence de champignons. Dix isolats de Heterobasidion parviporum Niemela & Korhonen et 425 isolats de Heterobasidion annosum (Fr.) Bref. ont ete soumis a des tests de compatibilite somatique pour determiner leur clonalite. Les conclusions suivantes ont ete tirees : (i) P. contorta est tres sensible a H. annosum et H. parviporum et les deux pathogenes causent le deperissement de P. contorta; (ii) H. annosum present dans les souches de P. sylvestris restantes de la rotation precedente peut effectivement se transmettre au P. contorta; (iii) les pathogenes peuvent former des clones territoriaux en constante expansion; (iv) les basidiospores des deux pathogenes colonisent les souches de P. contorta (infections primaires); (v) les clones de H. parviporum se propagent plus lentement que les clones de H. annosum; (vi) la propagation clonale est plus rapide a partir des souches oU sont etablies des infections secondaires qu'a partir des souches colonisees a la suite d'une infection primaire; (vii) H. annosum peut persister dans les souches de pin pendant au moins 26 ans; et (viii) on devrait envisager de traiter les souches pour maitriser les infections primaires causees par Heterobasidion. [Traduit par la Redaction] Mots-cles : pin tordu, Heterobasidion, infection primaire, infection secondaire., 1. Introduction Since the 1950s, the introduced lodgepole pine, Pinus contorta Dougl. ex Loudon, has become increasingly important in forestry in Northern Europe, and to date, hundreds of thousands of [...]

The spread of the ascomycete Hymenoscyphus fraxineus, causing dieback of common ash (Fraxinus excelsior) in Europe, is rapid and the damage is pronounced, as young ashes can perish over the course of only a few months following infection. The objective of this study was to investigate the rate and extent of lesion formation on young (5-8-year-old) ashes during a vegetation season in the hemiboreal zone in Latvia. Continuous surveys (with monthly intervals) of the health condition of 30 young ash and measurements of lesion area in three stands were performed during the vegetation season of 2015. From June to September of that year, the number of observed lesions gradually rose from 58 to 87. New lesions emerged on branches (55%, 0.5 per tree), top shoots (28%, 0.3 per tree), and stems (17%, 0.2 per tree), mostly appearing at the beginning of the observation period (45%, 52%, and 3% in June, July, and August, respectively). During the vegetation season, 20% of the existing and 28% of the newly-emerged lesions on branches, as well as 20% and 25% of top shoot lesions, respectively, reached the main stem. Some (< 20% of cases) transitions of lesions from the tops and branches to the stems were observed. The extension of lesions was significant until August, and ceased afterwards in a similar fashion in all stands. The mean extension of area significantly differed between the previously-existing and newly-emerged lesions. During the vegetation season, the new lesions expanded by 25.1 ± 4.8 cm2, whereas the existing ones grew by only 7.3 ± 1.1 cm2. The extension of the new lesions varied according to their location on a tree. The spread of emerging lesions on stems was considerably slower than on branches or top shoots (1.9 ± 0.7, 7.3 ± 1.5, and 14.5 ± 4.1 cm2 per lesion per month, respectively). During the studied vegetation season (summer), the overall health score of trees decreased twice, yet the relationship between heath status and development of lesions lacked significance.

: Root and butt rot is the most destructive disease of conifers in the Northern Hemisphere, but little is known about the dynamics of yield loss in stands of different ages, site types, and species composition. This study aimed to estimate butt rot incidence, causal fungi, and related wood yield loss in Picea abies (L.) H. Karst. stands in Latvia. A total of 24 745 stumps were examined on 318 forest sites, and 21.8% of them contained rot. There was a positive correlation between stand age and butt rot frequency. Proportion of other tree species in a stand had no influence on incidence of the rot, but significant differences were observed among different forest site types. The length of decay columns in 114 stems analysed was 6.6 ± 2.6 m on average. Based on the observed butt rot frequencies in Latvian P. abies stands of different age classes, volumes of decay-degraded wood in a fully stocked stand would comprise about 19.7 [m.sup.3] * [ha.sup.-1] at the age of 40 years, 57.4 [m.sup.3] * [ha.sup.-1] at 60 years, 54.9 [m.sup.3] * [ha.sup.-1] at 80 years, 63.1 [m.sup.3] * [ha.sup.-1] at 100 years, and 91.8 [m.sup.3] * [ha.sup.-1] at 120 years, corresponding to 6%-16% of a total standing volume. Resume: Le pourridie est la maladie la plus dommageable chez les coniferes dans l'hemisphere nord mais la dynamique des pertes de rendement selon l'?ge, le type de station et la composition en especes est peu connue. Cette etude visait a determiner l'incidence du pourridie, les champignons responsables et la perte de rendement en matiere ligneuse dues a cette maladie dans les peuplements de Picea abies (L.) H. Karst. en Lettonie. Au total, 24 745 souches ont ete examinees dans 318 stations et 21,8 % contenaient de la carie. Il y avait une correlation positive entre l'age du peuplement et la frequence du pourridie. La proportion d'especes compagnes dans le peuplement n'avait pas d'influence sur l'incidence de la carie mais des differences significatives ont ete observees entre les differents types de station. La colonne de carie avait une longueur moyenne de 6,6 ± 2,6 m dans les 114 tiges qui ont ete analysees. En se basant sur la frequence observee du pourridie dans les peuplements de P. abies de differentes classes d'?ge en Lettonie, le volume de bois carie dans un peuplement avec une densite relative adequate serait respectivement d'environ 19,7, 57,4, 54,9, 63,1 et 91,8 [m.sup.3] * [ha.sup.-1] a l'?ge de 40, 60, 80, 100 et 120 ans, ce qui correspond a 6-16 % du volume sur pied. [Traduit par la Redaction], Introduction Butt and stem rots are the most economically important diseases of Picea abies (L.) H. Karst. in Europe, especially in managed forests where cut stumps and wounds on living [...]

We have isolated and confirmed the identification of ash dieback fungus ( Chalara fraxinea, teleomorph Hymenoscyphus albidus) for the first time in Finland. In a preliminary analysis, considerable amount of genetic variation was detected among 20 Finnish (Åland and mainland Finland), one Latvian and 11 Estonian isolates, analysed by random amplified microsatellite (RAMS) markers. [ABSTRACT FROM AUTHOR]

Growth rates of H. annosum s.s. and H. parviporum were investigated in the functional sapwood of young Pinus sylvestris and Picea abies plants as an indicator of the relative susceptibilities of the hosts to these pathogens. The stems of 520 five-year-old P. abies and 321 four-year-old P. sylvestris plants were inoculated and the extent of infection determined 16 weeks later . H. annosum s.s . grew further than H. parviporum in P. sylvestris sapwood, while in P. abies, no differences between the two Heterobasidion spp. were found. Both H. annosum s.s. and H. parviporum spread faster in the sapwood of P. abies than in P. sylvestris. There was high within-host species variation in growth rates for both P. sylvestris and P. abies suggesting it may be possible to identify tree genotypes with lower susceptibility. [ABSTRACT FROM AUTHOR]

The occurrence of Chalara fraxinea, the fungus responsible for dieback of European ash ( Fraxinus excelsior), was investigated in the current and previous seed years collected from symptomatic trees in Latvia and Sweden using molecular techniques ( DNA extraction, ITS- PCR, Sanger sequencing). Molecular analysis of seeds revealed the presence of 30 different fungal taxa. Chalara fraxinea was detected in 8.3% of seeds tested from the current year originating from Latvia. The presence of C. fraxinea in seeds of F. excelsior is of great concern to phytosanitary protection authorities in countries outside the current zone of infestation. [ABSTRACT FROM AUTHOR]

Whether intraspecific phenotypic variation in saprobic fungi may be driven by the host of origin has received little attention. We addressed this issue by testing hypotheses using the model system Phlebiopsis gigantea, a wood destroying fungus associated with Picea abies and Pinus sylvestris, among others, and widely employed in practical forestry as a biological control agent. By examining approximately 60 sympatric P. gigantea isolates from both P. abies and P. sylvestris, we showed that the former grew in vitro significantly (P < 0.05) slower than the latter (average 5.56 mm/day vs. 6.84) while producing 1.8-fold significantly higher number of mitospores. An overall significant trade-off between these two phenotypic traits was detected, in particular for isolates originating from P. abies. Comparative inoculation experiments of a subsample of isolates and the assessment of mycelial growth in logs of both hosts allowed to reject the hypothesis that isolates are equally fit in terms of growth rate in wood of both hosts regardless of the host of origin. Tree models revealed that the growth rate of isolates was associated not only with the wood species in which the isolates were inoculated (P < 0.001), P. sylvestris being more rapidly colonized than P. abies, but also with the host of origin of isolates (P < 0.001). Results showed that P. gigantea isolates originating from different hosts differ phenotypically in terms of some key phenotypic traits demonstrating that a host-driven intraspecific phenotypic variation may occur in saprobic fungi., (© 2023. The Author(s).)

Treatment of conifer stumps with a control agent effectively prevents Heterobasidion spore infections in summer cuttings and protects the residual stand and the next tree generation from damage caused by Heterobasidion root rot. Thus far, stump treatment experiments have been carried out in mineral soils, and no information is available on the efficacy of stump treatment agents in boreal peatland conditions. In the present study, biological and chemical control agents ( Phlebiopsis gigantea and urea, respectively) were tested in Scots pine and Norway spruce stands subjected to thinning, cap cutting, and clearcutting on drained peatland in Central Finland. The control efficacy of urea was high in both spruce and pine stumps (on average 99.5 and 85.3%, respectively), while the efficacy of P. gigantea was highly variable on both tree species and ranged from full protection down to negative control effect, i.e., there were more Heterobasidion infections on the treated than untreated half of the stumps. The moisture content of the stump wood or the thickness of the peat layer did not affect the control efficacy of either control agent. These results emphasize a need for further studies to determine the reasons for the unsteadiness of the biological control in peatland conditions.

We examined differences in fine root morphology, mycorrhizal colonisation and root-inhabiting fungal communities between Picea abies individuals infected by Heterobasidion root-rot compared with healthy individuals in four stands on peat soils in Latvia. We hypothesised that decreased tree vitality and alteration in supply of photosynthates belowground due to root-rot infection might lead to changes in fungal communities of tree roots. Plots were established in places where trees were infected and in places where they were healthy. Within each stand, five replicate soil cores with roots were taken to 20 cm depth in each root-rot infected and uninfected plot. Root morphological parameters, mycorrhizal colonisation and associated fungal communities, and soil chemical properties were analysed. In three stands root morphological parameters and in all stands root mycorrhizal colonisation were similar between root-rot infected and uninfected plots. In one stand, there were significant differences in root morphological parameters between root-rot infected versus uninfected plots, but these were likely due to significant differences in soil chemical properties between the plots. Sequencing of the internal transcribed spacer of fungal nuclear rDNA from ectomycorrhizal (ECM) root morphotypes of P. abies revealed the presence of 42 fungal species, among which ECM basidiomycetes Tylospora asterophora (24.6 % of fine roots examined), Amphinema byssoides (14.5 %) and Russula sapinea (9.7 %) were most common. Within each stand, the richness of fungal species and the composition of fungal communities in root-rot infected versus uninfected plots were similar. In conclusion, Heterobasidion root-rot had little or no effect on fine root morphology, mycorrhizal colonisation and composition of fungal communities in fine roots of P. abies growing on peat soils.

We studied long-term effects of fertilization with wood ash on biomass, vitality and mycorrhizal colonization of fine roots in three conifer forest stands growing in Vacciniosa turf. mel. (V), Myrtillosa turf. mel. (M) and Myrtillosa turf. mel./Caricoso-phragmitosa (MC) forest types on peat soils. Fertilization trials amounting 5 kg/m(2) of wood ash were established 12 years prior to this study. A total of 63 soil samples with roots were collected and analysed. Ectomycorrhizal (ECM) fungi in roots were identified by morphotyping and sequencing of the fungal internal transcribed spacer (ITS) region. In all forest types, fine root biomass was higher in fertilized plots than in control plots. In M forest type, proportion of living fine roots was greater in fertilized plots than in control plots, while in V and MC, the result was opposite. Fifty ECM species were identified, of which eight were common to both fertilized and control plots. Species richness and Shannon diversity index were generally higher in fertilized plots than in control plots. The most common species in fertilized plots were Amphinema byssoides (17.8%) and Tuber cf. anniae (12.2%), while in control plots, it was Tylospora asterophora (18.5%) and Lactarius tabidus (20.3%). Our results showed that forest fertilization with wood ash has long-lasting effect on diversity and composition of ECM fungal communities.

The aim of this study was to assess belowground occurrence, persistence and possible impact of the biocontrol agent Phlebiopsis gigantea (Fr.) Jülich on soil fungi. Sampling of soil and roots of Picea abies (L.) H. Karst. was carried out at 12 P. gigantea-treated and five nontreated control sites representing 1- to 60-month-old clear-cuts and thinned forest sites in Finland and Latvia. The 454-sequencing of ITS rRNA from fine roots, humus and mineral soil resulted in 8626 high-quality fungal sequences. Phlebiopsis gigantea represented 1.3% of all fungal sequences and was found in 14 treated and nontreated sites and in all three substrates. In different substrates, the relative abundance of P. gigantea at stump treatment sites either did not differ significantly or was significantly lower than in nontreated controls. No significant correlation was found between the time elapsed since the tree harvesting and/or application of the biocontrol and abundance of P. gigantea in different substrates. In conclusion, the results demonstrate that P. gigantea occasionally occurs belowground in forest ecosystems but that stump treatment with the biocontrol agent has little or no impact on occurrence and persistence of P. gigantea belowground, and consequently no significant impact on soil fungi., (© 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.)