Alien forest pathogens and pests in the changing environment: focus on North Europe

Coordinator: Rimvydas Vasaitis, , SLU


Project background:

Galleries of Emerald ash borer. Photo: Audrius Menkis

Over recent decades, climate change has increased the risk of forest damage in the Nordic region, in particular caused by alien invasive forest pathogens and pests. A good example of emergence in Northern forests is the case of Diplodia sapinea in Sweden. The pathogen was reported for the first time in 2013 and was regarded innocuous as no associated damages were observed. However, 3 years after the first observation, D. sapinea was found associated with an unprecedented outbreak on pine. Recent detections in Estonia and Finland suggest an ongoing range expansion to the north. In following years, the disease emerged and caused notable losses in pine woodlands on Gotland Island.  It is assumed that climatic factors, as drought combined with high temperatures, predispose trees to attacks by the pathogen.

Initial observations indicated the expansion of several insects towards the north, e.g., Ips typographus, Monochamus spp., Tetropium castaneum, etc. The most characteristic disease in the region is canker of spruce, new emerging phenomenon also expanding north. For example, the spread of the canker in forests of Karelia resulted in decline and large-scale death of spruce stands. The situation is aggravated by the formation in diseased stands of reproductive centers of mentioned stem insect pests. Yet the exact identity of pathogens causing the disease is unclear. Preliminary results indicate that the key role in this process is played by new invasive species, presumably from the genus Corinectria.

Alien Emerald ash borer (EAB) constitutes threat for the existence of European ash, recently establishing in Ukraine, but also 1200 km north in St. Petersburg, thus closing to the borders of Estonia and Finland. Available studies demonstrate that climate has a notable impact on EAB populations, the development in the north being less effective. Furthermore, the work has been initiated on screening of ash for resistance to both EAB and the alien ash dieback disease (ADB). As a starting material for this, material from putatively ADB-resistant ash is being used, monitored, selected, sown/planted on Gotland within EU LIFE+ project ELMIAS, in collaboration with stakeholders. Those trees/sites were established to be used as an attempt for long-perspective mitigation effort of damage caused by ADB. Another example for mitigation of alien invasive pathogen, targeted by ELMIAS on Gotland, is Dutch elm disease (DED).


Overall long-term goal of the network:

Approaching Estonia and Finland. Ash trees killed by Emerald ash borer in St. Petersburg. Photo: Audrius Menkis

To establish/continue collaboration of north-European researchers tackling actual problems caused by emerging forest diseases and pests in relation to climate change, and to initiate related EU project proposal.


Activities 2023:

  1. Workshop/seminar on Gotland addressing issues outlined in the project background.
  2. Field excursions to pinewoods damaged by Diplodia, sites of putatively ADB-tolerant ash, and elm woodlands subjected to management of DED.