Facteurs édaphiques, dépérissement du chêne et infection par Collybia fusipes

International audienceCollybia fusipes is the cause of a root rot of oaks in Europe. Infection by the pathogen is site dependent and inconsistently correlated with crown deterioration. This study aimed at clarifying the relationship between soil factors and C. fusipes impact on tree health. The database of the Département de la Santé des Forêts, the forest health survey service, collected over the French forest during the last 12 years allowed us to perform a large scale study dealing with soil textures in which C. fusipes was reported to induce problems on Quercus robur and/or Q. petraea. Furthermore, a specific survey from 30 plots in north eastern France was carried out to determine which of the soil factors, such as texture, degree of waterlogging, presence and nature of a layer limiting rooting, carbon/nitrogen ratio, cation exchange capacity, or pH could be related to an increased risk of decline of pedunculate oaks infected by C. fusipes. The main results were that C. fusipes is preferentially distributed on coarse textured soils and that its impact on tree crown appearance also increased with the soil sand content

Dothistroma needle blight, weather and possible climatic triggers for the disease's recent emergence

Dothistroma needle blight (DNB), caused by the two fungi Dothistroma septosporum and D. pini, is a major disease of pines with a worldwide distribution. Increases in the incidence and severity of disease in areas where the disease has long been established and notable range expansions have both recently been observed. The aim of this review was to assess the relationship between DNB, weather factors and climate to better understand possible underlying causes of this recent intensification in disease. A substantial body of literature shows that the life cycles of the fungi are closely related to weather factors such as precipitation and temperature. Given the rapid response of DNB to favourable weather conditions, it seems plausible that changes in disease behaviour could be due to changes in climate. The recurrent El Ni~no-Southern oscillation (ENSO) phenomenon influences patterns of temperature and precipitation in many regions of the world, often resulting in warmer and wetter conditions than normal. We found that since the 1950s, four of the past five strong El Ni~no events appear to have coincided with reports of increased DNB activity on an intercontinental scale. The lack of long-term standardized data records limits our ability to fully interpret this relationship, but the projected future climatic conditions in the Northern Hemisphere appear to be increasingly favourable for the disease. Still, other areas of the world may become less favourable, and further research is required to be able to accurately predict DNB outbreaks and their impact on pine forests in the future.info:eu-repo/semantics/publishedVersio

Problèmes sanitaires des plantations artificielles de merisier

National audienc

What was old is new again: thermal adaptation within clonal lineages during range expansion in a fungal pathogen

Range-expanding species are expected to gain an increasing importance in the context of global change. They provide a great opportunity to study contemporary evolutionary changes and to unravel the mechanisms of evolution. Cryphonectria parasitica, the causal agent of chestnut blight, originating from Asia, has been spread since the beginning of the 20th century into different continents. We took advantage of the C. parasitica recent emergence in northern France to study the changes in population genetic structure and in phenotypic traits along this colonization and climatic gradient. Four hundred twenty-seven C. parasitica isolates were sampled in 47 chestnut sites in northern France. The C. parasitica outbreak in the north was found to be due to the expansion of five dominant clonal groups from southern France and to the emergence of a few rare recombined genotypes. The evolutionary changes during C. parasitica range expansion were studied by analyzing phenotypic changes in isolates from the same clonal lineage, with or without a geographic shift. Growth rates were assessed in vitro, at four temperatures. The northern isolates grew faster at 12 and 15°C and more slowly at 28 and 32°C than the southern isolates. These results strongly suggest local adaptation to low temperatures in C. parasitica, with a trade-off of slower growth at high temperatures. They also reflect the high evolutionary potential of C. parasitica along a colonization gradient and show that clonal evolution is not a limitation for the rapid thermal adaptation of this invasive fungal species

A worldwide perspective on the management and control of Dothistroma needle blight

Dothistroma needle blight (DNB) caused by Dothistroma septosporum and Dothistroma pini is a damaging disease of pine in many countries. The disease led to the abandonment of planting susceptible Pinus species in parts of Africa, Asia, Australasia, Europe and North America. Although the disease can be effectively controlled using copper fungicides, this chemical is only routinely applied in forests in New Zealand and Australia. Other management tactics aimed at making conditions less favourable for disease development, such as thinning or pruning, may be effective on some, but not all, sites. Disease avoidance, by planting non-susceptible species, is the most common form of management in Europe, along with deployment of hosts with strong disease resistance. Although D. septosporum is present almost everywhere Pinus is grown, it is important that an effort is maintained to exclude introductions of new haplotypes that could increase virulence or enable host resistance to be overcome. A global strategy to exclude new introductions of Dothistroma and other damaging forest pathogens, facilitated by collaborative programmes and legislation, is needed.This study was partially supported by the EU COST Action FP1102 DIAROD (Determining Invasiveness and Risk of Dothistroma, http:// www.cost.eu/COST_Actions/fps/FP1102)http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1439-03292017-10-31hb2017Forestry and Agricultural Biotechnology Institute (FABI)GeneticsPlant Scienc

A worldwide perspective on the management and control of Dothistroma needle blight

Dothistroma needle blight (DNB) caused by Dothistroma septosporum and Dothistroma pini is a damaging disease of pine in many countries. The disease led to the abandonment of planting susceptible Pinus species in parts of Africa, Asia, Australasia, Europe and North America. Although the disease can be effectively controlled using copper fungicides, this chemical is only routinely applied in forests in New Zealand and Australia. Other management tactics aimed at making conditions less favourable for disease development, such as thinning or pruning, may be effective on some, but not all, sites. Disease avoidance, by planting non- susceptible species, is the most common form of management in Europe, along with deployment of hosts with strong disease resistance. Although D. septosporum is present almost everywhere Pinus is grown, it is important that an effort is maintained to exclude introductions of new haplotypes that could increase virulence or enable host resistance to be overcome. A global strategy to exclude new introductions of Dothistroma and other damaging forest pathogens, facilitated by collaborative programmes and legislation, is needed

Climate change and forest diseases

As climate changes, the effects of forest diseases on forest ecosystems will change. We review knowledge of relationships between climate variables and several forest diseases, as well as current evidence of how climate, host and pathogen interactions are responding or might respond to climate change. Many forests can be managed to both adapt to climate change and minimize the undesirable effects of expected increases in tree mortality. We discuss four types of forest and disease management tactics – monitoring, forecasting, planning and mitigation – and provide case studies of yellow-cedar decline and sudden aspen decline to illustrate how forest diseases might be managed in the face of climate change. The uncertainties inherent to climate change effects can be diminished by conducting research, assessing risks, and linking results to forest policy, planning and decision making