Jonas Rönnberg

Bio: Jonas Rönnberg is an academic researcher from Swedish University of Agricultural Sciences. The author has contributed to research in topics: Heterobasidion annosum & Heterobasidion. The author has an hindex of 16, co-authored 35 publications receiving 628 citations.

Effectiveness of treatment of Norway spruce stumps with Phlebiopsis gigantea at different rates of coverage for the control of Heterobasidion

Abstract: Summary The natural establishment of the root and butt rot causing fungus Heterobasidion annosum s.l. on Norway spruce (Picea abies) thinning stumps treated with Phlebiopsis gigantea was investigated on seven sites in southern Sweden. The trees were cut during summertime and the stumps were treated with different patterns simulating the effect of mechanical stump treatment with a single-grip harvester. Sampling was conducted 3 and 12 months after treatment. At both samplings, the best control was obtained when 100% of the stump surface was covered by P. gigantea: in contrast, untreated control stumps showed the highest incidences of H. annosum s.l. infection at both sampling times. However, 30 and 26% of the fully covered stumps at the first and second samplings, respectively, were diseased, and question the efficacy of treating Norway spruce stumps with this biological control agent in Sweden. Resume L’etude porte sur l’etablissement naturel d’Heterobasidion annosum s.l. sur des souches d’eclaircies d'Epicea commun traitees avec Phlebiopsis gigantea, dans sept sites du sud de la Suede. Les arbres ont ete abattus pendant l’ete et traites selon differentes modalites simulant le traitement mecanique des souches par un combine d'exploitation a une seule pince. L’echantillonnage a ete realise trois et douze mois apres traitements. Quelle que soit la date d’echantillonnage, la meilleure efficacite a ete obtenue quand la surface totale de la souche avait ete traitee avec P. gigantea et la plus forte incidence d'infection par Heterobasidion chez les temoins non traites. Toutefois, meme chez les souches totalement traitees, des taux de 30% et 26% d'infection ont ete observes respectivement aux deux dates d’echantillonnage, ce qui pose la question de l'efficacite de ce type de traitement des souches d'Epicea commun en Suede. Zusammenfassung An sieben Standorten in Sudschweden wurde die naturliche Besiedelung von Fichtenstumpfen (Picea abies) mit Heterobasidion annosum s.l. in Durchforstungen nach einer Behandlung mit Phlebiopsis gigantea untersucht. Die Baume wurden wahrend des Sommers gefallt und die Stumpfoberflachen nach unterschiedlichen Mustern behandelt, welche die mechanische Stumpfbehandlung mit einem einarmigen Vollernter simulieren sollten. Die Stumpfe wurden drei und zwolf Monate nach der Behandlung beprobt. An beiden Probeterminen wurde die beste Wirkung bei hundertprozentiger Bedeckung der Stumpfoberflache mit P.gigantea erzielt. Unbehandelte Stumpfe hatten jeweils die hochsten Infektionsraten mit Heterobasidion. Jedoch waren 30% bzw. 26% der Stumpfe mit vollkommener Oberflachenbehandlung am ersten bzw. zweiten Probetermin ebenfalls mit Heterobasidion infiziert, was Fragen nach der Wirksamkeit dieser Behandlung von Fichtenstumpfen in Schweden aufwirft.

Modeling infection and spread of Heterobasidion annosum in even-aged Fennoscandian conifer stands

Abstract: Heterobasidion annosum (Fr.) Bref. s. lato causes severe damage to forests. This study describes a model for simulating the infection and spread of Heterobasidion spp. in stands of Picea abies (L.) Karst. and Pinus sylvestris L. The model includes submodels for stand dynamics (plot simulation, growth and yield, and cross-cutting of trees) and disease dynamics: (i) spore infection, (ii) stump colonization, (iii) colonization of stump roots, (iv) vegetative transfer to tree roots, (v) spread of disease in tree roots, (vi) spread of decay in stems, and (vii) disease effect on tree growth and survival. To illustrate the model, a simulation was carried out on a Swedish Norway spruce stand where logging occurred during the high-risk season for spore infection. The model provides a means of incorporating the impact of root disease into forest planning. A change of parameters indicated that model predictions were sensitive to the spread rate and presence of initial disease centers. Further research is called for in areas related to the development of coarse root systems of various tree species and the probability and rate of transfer of disease from various sources of inoculum to healthy trees.

Reducing the risk of invasive forest pests and pathogens : Combining legislation, targeted management and public awareness

Abstract: Intensifying global trade will result in increased numbers of plant pest and pathogen species inadvertently being transported along with cargo. This paper examines current mechanisms for prevention and management of potential introductions of forest insect pests and pathogens in the European Union (EU). Current European legislation has not been found sufficient in preventing invasion, establishment and spread of pest and pathogen species within the EU. Costs associated with future invasions are difficult to estimate but past invasions have led to negative economic impacts in the invaded country. The challenge is combining free trade and free movement of products (within the EU) with protection against invasive pests and pathogens. Public awareness may mobilise the public for prevention and detection of potential invasions and, simultaneously, increase support for eradication and control measures. We recommend focus on commodities in addition to pathways, an approach within the EU using a centralised response unit and, critically, to engage the general public in the battle against establishment and spread of these harmful pests and pathogens.

Comparison of five strains of Phlebiopsis gigantea and two Trichoderma formulations for treatment against natural Heterobasidion spore infections on Norway spruce stumps

Abstract: In an experiment established on three Norway spruce sites in southern Sweden, the ability of five strains of Phlebiopsis gigantea, including the commercial strain Rotstop®, and two Trichoderma formulations to control natural Heterobasidion spp. spore infections was compared. At each site 160 trees were felled, and the resulting stumps were treated with spore suspensions of the seven fungal preparations. Twenty stumps at each site were left untreated as control stumps. When sampled 9 months after treatment, two of the P. gigantea strains (1984 and 1985) were the most effective at preventing infection by Heterobasidion spp. The other three P. gigantea strains were less effective, and two Trichoderma formulations did not significantly reduce Heterobasidion spp. infections.

Effect of Temperature

Abstract: A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Consequences of climate change for biotic disturbances in North American forests

Abstract: About one-third of North America is forested. These forests are of incalculable value to human society in terms of harvested resources and ecosystem services and are sensitive to disturbance regimes. Epidemics of forest insects and diseases are the dominant sources of disturbance to North American forests. Here we review current understanding of climatic effects on the abundance of forest insects and diseases in North America, and of the ecological and socioeconomic impacts of biotic disturbances. We identified 27 insects (6 nonindigenous) and 22 diseases (9 nonindigenous) that are notable agents of disturbance in North American forests. The distribution and abundance of forest insects and pathogens respond rapidly to climatic variation due to their physiological sensitivity to temperature, high mobility, short generation times, and high reproductive potential. Additionally, climate affects tree defenses, tree tolerance, and community interactions involving enemies, competitors, and mutualists of insects ...

A proposed unified framework for biological invasions.

Abstract: There has been a dramatic growth in research on biological invasions over the past 20 years, but a mature understanding of the field has been hampered because invasion biologists concerned with different taxa and different environments have largely adopted different model frameworks for the invasion process, resulting in a confusing range of concepts, terms and definitions. In this review, we propose a unified framework for biological invasions that reconciles and integrates the key features of the most commonly used invasion frameworks into a single conceptual model that can be applied to all human-mediated invasions. The unified framework combines previous stage-based and barrier models, and provides a terminology and categorisation for populations at different points in the invasion process.

Facts from figures

Abstract: Contrary to NAFTA’s stated objectives, the Mexican economy has failed in its promise to create quality jobs and to address the erratic and feeble growth of workers’ income. Mexico’s global trade deficit is growing despite its increasing trade surplus with the United States, and the race to the bottom set off by NAFTA has meant nothing better than low-wage work for most Mexican workers, while benefiting large companies, the financial sector, and a thin layer of administrative and professional workers who are earning high salaries. Employment has become increasingly precarious overall, the agricultural sector has suffered a large and steady loss of employment, and real salaries remain below the levels of the early 1990s, as Mexico’s dependence on global imports grows.

Conifer root and butt rot caused by Heterobasidion annosum (Fr.) Bref. s.l.

Abstract: SUMMARY The root and butt rot caused by Heterobasidon annosum is one of the most destructive diseases of conifers in the northern temperate regions of the world, particularly in Europe Economic losses attributable to Heterobasidion infection in Europe are estimated at 800 million euros annually The fungus has been classified into three separate European intersterile species P ( H annosum ), S ( H parviporum ) and F ( H abietinum ) based on their main host preferences: pine, spruce and fir, respectively In North America, two intersterile groups are present, P and S/F, but these have not been given scientific names The ecology of the disease spread has been intensively studied but the genetics, biochemistry and molecular aspects of pathogen virulence have been relatively little examined Recent advances in transcript profiling, molecular characterization of pathogenicity factors and establishment of DNA-transformation systems have paved the way for future advances in our understanding of this pathosystem Taxonomy: Heterobasidion annosum (Fr) Bref, H parviporum Niemela & Korhonen and H abietinum Niemela & Korhonen; kingdom Fungi; class Basidiomycotina; order Aphyllophorales; family Bondarzewiaceae; genus Heterobasidion Identification: presence of the fungus fruit bodies, basidiocarps whitish in the margins, upper surface is tan to dark brown, usually irregular shaped, 35 ( − 7) cm thick and up to 40 cm in diameter; pores 5‐19, 7‐22 and 13‐26 mm 2 for the P, F and S groups, respectively Small brownish non-sporulating postules develop on the outside of infected roots Asexual spores (conidiospores) are 38‐66 × 28‐50 µ m in size Mating tests are necessary for identification of intersterility groups Host range: The fungus attacks many coniferous tree species In Europe, particularly trees of the genera Pinus and Juniperus (P), Picea (S), Abies (F) and in North America Pinus (P) and Picea , Tsuga and Abies (S/F) To a lesser extent it causes root rot on some decidous trees ( Betula and Quercus ) Disease symptoms: symptoms (eg exhudation of resin, crown deterioration) due to Heterobasidion root rot in living trees are not particularly characteristic and in most cases cannot be distinguished from those caused by other root pathogens Heterobasidion annosum sl is a white rot fungus Initial growth in wood causes a stain that varies in colour depending on host tree species Incipient decay is normally pale yellow and it develops into a light brown decay to become a white pocket rot with black flecks in its advanced stage Control: silvicultural methods (eg stump removal), chemicals (urea, borates) and biological control agent ( Phlebiopsis gigantea , marketed as PG Suspension® in the UK, PG IBL® in Poland and Rotstop® in Fennoscandia) are commonly used approaches for minimizing the disease spread