Pine wilt nematode in focus: Methods for diagnosis, control, and extermination
The pine wilt nematode (PWN), Bursaphelenchus xylophilus, originates in North America, where it is unobtrusive, and is transported via international trade to different countries. Contact with new host tree species in new climate zones has devastating consequences: nematode infestation can result in pine wilt, which can lead to rapid dieback of susceptible tree species. In living trees the nematode infects and feeds on living cells, thereby causing defensive reactions as well as the blocking of vascular tissue which at advanced stages can cause wilting and subsequent death of the tree. Nematodes can reproduce very rapidly - one generation develops in four days - and spread quickly throughout the tree, where trunk, limbs and roots become infected.|
The REPHRAME project gathers internationally recognized research, which should fill the considerable gaps in our understanding of this globally significant pathogen. A PWN Tool Kit, which integrates newly generated and current knowledge, should provide affected sites in the EU and other lands with better methods for combatting PWN.
Serious threatThe pine wilt nematode and associated pine wilt is a serious threat for our conifer forests. In Japan, where in 1905 the disease was first detected, the nematode has caused timber damage of 26 million m³ since 1945. Pine wilt still causes a widespread dieback of pine trees there. Millions of trees are also victims of the disease in China, Korea and Taiwan. A similar situation can be observed in Portugal, where the nematode first occurred in 1999. Despite intensive extermination campaigns the infested area has increased further, the island of Madeira has also been hit in the meantime.
After the establishment of a bridgehead on the continent, there were grounds to fear that the disease would spread to other parts of Europe. In order to effectively restrict or - where possible - exterminate the pine wilt nematode, it is important to obtain exact knowledge of its behaviour and dynamics in the infected tree.
Of fundamental importance is the understanding of the interaction between nematodes, their host trees and their vectors: longhorn beetles of the genus Monochamus. These beetles transmit the nematode during their maturation feeding and larval feeding on young shoots on uninfected host trees. Through their flight they contribute to the areal spread of the nematode, if they are transported as passengers in infected wood, new areas of infestation can develop over long distances.
Activities in project REPHRAMEREPHRAME studies in detail how nematodes move between and inside host trees. The potential, and the necessary conditions, for the spread of the nematode with and without its vector Monochamus spp. was studied. Based on this, the PWN Tool Kit offers management options to diagnose and combat nematode attacks.
Not all trees die when infected with the nematode. Models are being developed to predict the degree an outbreak of the lethal wilt can occur in different regions and climate scenarios. These models will be linked to others, which will simulate the spread of the nematodes through vectors and human activities.
Support for practitioners
A number of results from REPHRAME will be useful for authorities, forest owners and traders:
The Project partnersThe project is funded through the EU Framework Programme FP7, with eleven research organisations from eight countries (China, Germany, UK, France, Norway, Austria, Portugal, and Spain) cooperating on it. There are further links to partners in Japan, Canada, and the USA.
Working priorities in the framework of REPHRAME at the BFWThe vector for the pine wilt nematode on the Iberian Peninsula is the pine sawyer beetle, Monochamus galloprovincialis. Two further species of the genus are abundant in Central Europe which could be potential vectors: the sawyer beetle M. sartor and the small white-marmorated longhorn beetle M. sutor, both of which principally develop in spruces here. Spruces can also become host trees for pine wilt nematodes. Even where it may not lead to an outbreak of wilt - this has mainly been observed on pine up to now - the spruce can provide a reservoir for nematodes, whose development is then possible. Both beetle species can then function as vectors, as both can also develop in pine.
Our work within the framework of the project should deliver new data on the biology of M. sartor and M. sutor. Phenology, breeding success and flight patterns will be examined. The Data will be inputted into the various models which have been developed during the project. A further important point is the chemical ecology of M. sartor, which remains unknown. In cooperation with Spanish and British project partners we are examining the pheromonal communication of this species, and are testing various attractants and traps for monitoring. Preliminary results show, that an attractant developed for M. galloprovincialis from tree-produced substances, components of bark-beetle pheromones, and a Monochamus pheromone component, also attracts M. sartor. Further tests should determine, if other substances can increase its attractiveness. The goal is to make available a trapping system to observe the flight of vectors.
Projekt-coordinator: Prof. Hugh Evans, Forest Research in Wales
Bundesforschungs- und Ausbildungszentrum für Wald, Naturgefahren und Landschaft (BFW)
Austria, 1131 Wien, Seckendorff-Gudent-Weg 8 | Tel.: +43 1 878 38-0
Autor: Hoch G.