Invasive pathogens demand sophisticated warning systems
Invasive forest pathogens are already here, and more of them can be expected in the future. Researchers fear that a warmer climate and more intensive trade will increase the chance of diseases arriving in the region that may become a true threat to Noardic forests. A warning system is needed to combat the pathogens in a timely manner.
The SNS-supported project “Risk assessment and establishment of a system to address potential pathogens in Nordic and Baltic forestry as a result of climate change” presented a proposal in July 2012 to establish a monitoring and warning system for forest pathogens. The background is that anticipated changes in climate, together with globalisation of trade, are expected to increase new introductions of forest pathogens in the Nordic and Baltic region. The project was initiated by SNS to deliver the actions listed in the Selfoss declaration (see another article in this edition of News & Views).
New pathogens a threat
Pathogens can be spread in many ways, including through air-borne fungal spores or by insect vectors. Such natural invasion can be expected to increase as conditions within the Nordic countries become suitable for a wider range of pathogens due to a warmer climate. Pathogens can also be spread with human help as passengers on nursery stock or wood products traded on the international market.
The project report highlights a number of potential pathogens that have been observed in the region or are expected to be found in the near future. The genus Phytophthora includes several examples of aggressive species that have caused severe damage elsewhere in the world. Many species have been observed in the Nordic and Baltic countries, posing a potential threat to both conifers and broadleaved trees.
Sphaeropsis sapinea is an important pathogen on conifers throughout the world. It is established in southern Europe but has recently been observed in Estonia on Pinus nigra trees. The pathogen is known to cause damage to a large number of coniferspecies, and may also become a threat to trees in the Nordic forests as it spreads further north.
The rust fungi Endocronartium harknessii causes the western gall rust or pine-pine gall rust in North America, but is currently not found in Europe. If introduced to the Nordic and Baltic region, this pathogen could have a devastating impact.
Native pathogens may proliferatea
Another risk factor with a warmer climate is that already established pathogens may become more aggressive or more widely spread. Examples of common pathogens which are predicted to change with the climate are Heterobasidion spp. (root rots), Melampsora pinitorqua, Gremmeniella abietina and Cronartium flaccidum.
Lophodermium seditiosum (pine needle cast) is another pathogen common in southern Fennoscandia, but recent sampling of pine needles has also been found it northern Sweden. This species has spread northwards, causing more disease in northern areas as the climate warms, but it may become less harmful in the south due to drier summers.
A warmer climate can also affect insect vectors. One example is Ophiostoma novo-ulmi, which causes Dutch elm disease. The fungus is carried by elm bark beetles (Scolytus spp.), whose distribution is limited today. With a warmer climate, this insect may migrate northwards and spread the disease over the entire range of elm trees. The need to take action
The pathologists suggest a regionwide scheme to help optimise management and reduce the spread of pathogens. The key elements of such a scheme should include legislation and management plans, a monitoring system, competence building and a strategy for enhancing the dissemination of information about forest pathology. There is also a need for further research. The executive recommendations are presented in the final report. Some examples of recommended actions:
- Improved phytosanitary regulations for imported plants and wood material
- Restrictions on import of high risk genera (such as Rhododendron)
- A framework for the detection and monitoring of pathogens, including the use of spore trapping and sentinel plantings that target high risk sites (e. g. ports, nurseries, airports, popular tourist areas), in combination with widespread forest monitoring
- More training of plant health officials
- Training for forest owners and forest professionals carrying out forest health surveys.
Project leader and contact: Professor Jan Stenlid, jan. stenlid@slu.se
Participants:
Sweden: Jan Stenlid, Rimvydas Vasaitis, Elna Stenström, Johanna Boberg and Anna Hopkins
Denmark: Iben M. Thomsen
Finland: Arja Lilja, Jarkko Hantula
Norway: Halvor Solheim
Iceland: Halldór Sverrisson
Latvia: Talis Gaitnieks
Estonia: Rein Drenkhan
Lithuania: Vaidas Lygis
Download the final report “Risk assessment and establishment of a system to address potential pathogens in Nordic and Baltic forestry as a result of climate change” (pdf), compiled by Anna Hopkins and Johanna Boberg.
From News and Views no 7, 2012 (www.nordicforestresearch.org)
