Foreign fungi are invading nation

The fungi are understood to have migrated north of the Border because of the increasingly mild winters, which have led to an extension of the traditional autumn mushroom season by as much as four weeks in the past 15 years, The Scotsman has learned.

Professor Roy Watling, the former head of mycology at the Royal Botanic Garden, Edinburgh, and one of the country’s leading experts on mushrooms, has made the discoveries over the past two years, with two species being discovered in the back garden of his Edinburgh home.

Some of the specimens have been shown to be parasitic, requiring a host plant to grow on, and are now hitting plants that have previously remained free of such attack.

It is feared their arrival could upset the delicate ecological balance of Scotland’s wilderness, with potentially dire consequences for some plant species.

Many of the new species are rare, and as a result have no common names, unlike the more familiar edible species such as wood blewits and chanterelles.

Only two of the species actually conform to the traditional mushroom shape. Leucopaxillus rhodoleucus, a classic white species that resembles the traditional field mushroom, is generally considered a Mediterranean variety. Boletus pulverulentus belongs to the Bolete family - the same order to which the penny bun or cep belongs.

Prof Watling said: "Changes in our climate are allowing some fungi to possibly jump hosts, and these more parasitic fungi could pose quite serious implications for species that have always existed up here and not been under attack.

"One of these is rhododendrons, which did not have mildew until the last ten years. Now you can see them plastered with it, and again one suspects that this is due to either milder climate conditions, or people who visit nurseries who buy a lot of plants and things then get mixed up. Plants are coming up from nurseries in the south of England and being transplanted in Scotland.

"With the milder winters that allows these species to establish themselves and attack plants which have previously had no such parasites, and it is changing the ecosystem."

The remaining four species are all parasites.

One in particular, Phellinus ferreus is a bracket or shelf fungus which has been found growing on decaying mature trees and has the capacity to inflict extraordinary damage on the wider environment because it releases ozone-damaging chemicals.

Prof Watling said: "This species is a member of a family which is calculated worldwide to produce 160,000 metric tonnes of chlorinated fluorocarbons (CFCs) annually. That’s more than the entire surface area of the Pacific and Atlantic Oceans combined.

"Having found that out for one family, it shows our ignorance of what a large number of fungi do in our ecosystems."

He added: "Ten or 15 years ago the mushroom season would be well over by now. The discovery of all these new species to Scotland is another indicator of a change in the climate. People can argue that this change is correlated with climatic warming, but I couldn’t say."

However, Professor Geoffrey Boulton, a leading expert on long-term climate change at Edinburgh University, believes the changes that underlie the shift in species are "the real cause for concern".

He said: "There is very little doubt that the growing season has been extending. The time of first flowering of many plants has also been shown to have advanced very significantly over the last 50 years.

"If you take a very large variety of species, which respond to many different environmental factors, they together appear to tell a similar tale, which is the growing season has been lengthening.

"Records of the length of the growing season are almost certainly a reflection of the trend of underlying warming in the northern hemisphere, which has been particularly strong in the last 100 years and, if set against the last 1,000 years, stands out very clearly indeed.

"On the basis of evidence elsewhere and the reality of global warming, this is yet another sign of it," he added. "We should be concerned. In relation to global warming, the Earth has never been in this territory before. In its current configuration with a concentration of the atmosphere which is almost twice that which, based on records, normally happens in warm periods like the present."

MUSHROOMS ON THE MOVE

Leucopaxillus rhodoleucus: a classic white species that resembles the traditional field mushroom. It is considered a Mediterranean variety. It has now been found at the Royal Botanic Garden at Dawyck, Peebleshire, only the second time it has been spotted in Britain after it was discovered growing in the Home Counties.

Boletus pulverulentus: belongs to the Bolete family - the same order as the penny bun or cep. Has grown south of the Border but has never been seen in Scotland before. It has now established itself in the warmer and milder climate of Scotland’s western oak woodlands.

Erysiphe orontii: has also been found in Edinburgh gardens on the periwinkle family of plants. Many ornamental garden plants, including rhododendron, oleander, frangipani, allamanda and mandevilla, belong to the periwinkle family, and they could now be vulnerable to attack from the fungi, which appears on the leaves like a mould.

Puccinia distincta: another leaf mildew which can be seen as small orange dots on lawn daisy leafs, could also have been introduced by plants from England.

Pulcherrimum caeruleum: is a vivid purple mould "crust fungus" which has been found growing on decaying hazel branches. It has most likely been introduced with wattle hurdles from the south of England and has only just made its appearance when that wattle started to rot in Professor Watling’s back garden. The trade in gardening products and plant material is allowing these fungi to move around.

Phellinus ferreus: a bracket or shelf fungus which has been found growing on decaying mature trees and has the capacity to inflict extraordinary damage on the environment as it releases ozone-damaging chemicals.