An acorn of the Oregon oak (Quercus garryana), a native of Northwest America, which has been infested with fungi and suffered feeding damage through weevil larvae.


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World-wide tree seed trade is not as safe as previously assumed. Researchers of the Centre for Agriculture and Bioscience International (CABI), the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and other institutions have demonstrated that distributing seed can also spread numerous harmful insects and fungi, which present a major risk to trees and forest ecosystems.

Non-indigenous insect pests and pathogenic fungi constitute one of the greatest threats to trees and forest ecosystems world-wide. Such harmful organisms can significantly disturb the forest ecology and cause economic losses. In North America, for example, the emerald ash borer (Agrilus planipennis) destroyed the ash trees growing there across extensive areas. This insect has since already infested ash in Western Russia and is thus causing a threat to European ash species. In a similar manner, early in the twentieth century, the pathogenic fungus Cryphonectria parasitica almost exterminated the indigenous American chestnut, which considerably changed the tree composition of forests that had originally been rich in chestnut trees.

During the last few years, Iva Franić, René Eschen and Marc Kenis of CABI as well as researchers from WSL and other institutions have examined the insects and fungi on forest trees for the first time. In the journal Ecological Applications, the scientists point out that the infestation rates among seeds of some tree species are “alarmingly high”.

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