According to mycologist Leho Tedersoo of the University of Tartu, the most prevalent non-native fungal species in Estonia are pathogens or fungal diseases. "This bolete variety is quite unusual in that it is a rapidly spreading edible fungus with a large fruiting body," Tedersoo told ERR.

However, in the world of mushrooms, Tedersoo says, it is not always easy to define what is considered non-native. "Many fungi have partner or host plants," the mycologist said.

The fact that non-native fungi do not have to compete with other plants and animals for a place in the new ecosystem helps their spread. "There is a significantly greater diversity of life among microorganisms. They only need suitable soil, climate and host plants," Tedersoo said.

It's a different story with fungal diseases. "They usually live far away from Estonia and when they arrive here, they find a so-called naive host, which has not adapted to the pathogen and is defenseless against it. An example of such a non-native species is Hymenoscyphus fraxineus, an ascomycete fungus that causes ash dieback, which arrives in Estonia with timber from East Asia," the scientist said.

Logging contributes to the spread of non-native species

Tõnu Ploompuu, a botanist and mycologist at Tallinn University, said that the new bolete is already a common species in Estonian coastal forests. "Of course, it is very difficult to study changes in the fungi, both in terms of the fungal mycelium hidden in the soil and the number of fruiting bodies, which appear very unstable from year to year," he told ERR.

"It is obvious that by associating with the pine roots, boletes leave less space for other symbiotes. Other non-native fungi are often associated with non-native trees only and do not compete directly with native fungi in our forests," he explained.

According to Ploomuu, bark and vegetative mulch areas in Estonian forests are known habitats of non-native species. "These have not been specifically monitored in Estonia in the last decade, and previously there were no known non-native species here. Gardens are also important in the spread of non-native fungus species. Several tropical fungus, for example, are transmitted by pot plants, but these are would not survive in the wild," the mycologist said.

Ploomuu explained that degraded land is favorable for the introduction of new species. "In such places, these new species can easily find an empty place to grow. Invasive species can also be encouraged by clear-cutting and large-scale disturbance of forest soils by machinery. The quick spread of invasive plant species is also common in clear-cuts, which is not the case in more environmentally friendly logging places," the scientist said.

100 kilometers per year

Tedersoo said on "Vikerhommik" that the new bolete is currently spreading in Estonia at a rate of up to 100 kilometers per year. "It was most likely transported to Europe in pine cones from America. Lithuania was probably one of the first places of arrival. It first moved from exotic pines to common pines in Lithuania, and it has also successfully expanded to Estonia along sand coastal pines," the professor said.

He said that there is nothing to do but accept the new species as inevitable: "There is nothing we can do to prevent it from spreading." Fortunately, the new mushroom species is non-toxic and edible, thus this inescapable reality is currently favorable to mushroom enthusiast, Tedersoo said.

Aureoboletus projectellus has white or pinkish flesh and a slightly acidic, even citrusy flavor. It has no smell and, when cut, the body does not turn blue. During cooking, the mushroom turns yellowish-brown.

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