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The report reads as the record of a seriously ill patient. Coleoptera, fungi and bacteria cause considerable problems for the Swiss forest. This can be seen in the "Forest Conservation Review" recently published by the Department of Forest Protection Issues of the Swiss Federal Research Institute WSL in Birmensdorf. The "medical record" begins with the bark beetle, which becomes more and more friendly on stressed spruces. It was helped by the hot summer of last year and the storm damage suffered by Burglind and Friederike in the spring, which left a lot of fresh broodwood behind them. The amount of beetle wood is increasing again – it remains well below that of peak years from 2001 to 2006, but much more than in 1998, a year before storm Lothar, responsible for the late outbreak of bark beetles. "A renewed Lothar could further increase the infestation of beetles than at the time," says Valentin Queloz, an expert in forest conservation at WSL
Annual temperature will continue to increase with climate change in the coming decades. Longer droughts like this year will become the norm if global warming can not be stopped. For the bark beetle that is rosy prospects. For the Swiss forest, which consists essentially of spruce, it can become a great danger. However: The beetle belongs to the spruce forest of the ecosystem. It gives a chance to younger generations of trees by attacking old and weak spruces. Foresters can regulate the development of the beetle if they remove beetles in time.
Hope for ash trees
The bark beetle is therefore not at the top of the list of the most dangerous pests. They are rather introduced organisms such as the fungus Hymenoscyphus fraxineus. The pathogen reached East Asia from Poland in the 1990s and then spread rapidly throughout Europe. "Theoretically, a single infected leaf stem, which was perhaps between imported Chinese pavers, was sufficient for the introduction," write ETH researchers Ottmar Holdenrieder and Marco Pautasso in an article on forest health.
The fungus is responsible for the dying ashes in Switzerland, which spread rapidly to the southern border for ten years. Experts estimate that more than 90% of ash trees could die. "Ash is the second most common deciduous tree species after beech in Switzerland and plays an important ecological and economic role," says Valentin Queloz, WSL researcher
. In a survey conducted by the WSL in several cantons last year, 367 tolerant ash trees were reported. Resistance is currently being studied in Birmensdorf. "The ash rescue in Switzerland is based on these more resilient trees," says the WSL researcher
Switzerland benefits from Italy
This also applies to the chestnut wasp . She also comes from China and was discovered for the first time in Ticino in 2009. He lets the chestnut shoots die. The production of marroni is thus massively reduced. Italy and France reacted actively by releasing a natural wasp enemy, the parasitic parasitic wasp.
"Switzerland is reluctant in this respect, it gave up, because it can not be ruled out that parasitic wasps also have other important insects," says Queloz. Nevertheless, Switzerland benefits from the intervention. The common wasp also is widespread on the northern side of the Alps and has a positive effect.
Computer graphics: Bark beetles reproduce more strongly
Enlarge the graphic
Another example of a successful fight is the history of the Asian longhorn beetle. The animal is one of the most dangerous quarantine pests in the world. This means that the introduction and spread should be avoided urgently. The beetle can kill any type of deciduous wood in a few years. He was first brought with packaging materials from China to the United States and Canada, later he arrived in Austria, France and Italy. In Switzerland, the first beetles were discovered in 2011, while four free infestations are known. Two infestations were successfully eradicated. In Winterthur, this has been successful in four years. The destruction cost the city of Winterthur and the canton of Zurich about 3.3 million Swiss francs
Most of the pests integrate into the forest ecosystem and are not symptomatic. But some may weaken forest communities if they do not intervene in time. Prevention is also one of the most important measures to prevent the worst. "Unfortunately, the next invasive organism usually reaches us as a stranger," says the WSL researcher. Import controls at customs and control should prevent this as much as possible.
Next Threat
So-called "guardian" plantations are very promising. The goal of the International Sentinel Network's program is to grow a large number of native and alien tree and plant species in botanical gardens and nurseries around the world to detect diseases and diseases. pests at an early stage. In Switzerland too, various nurseries have to be built for this purpose. "If you knew more in advance, you probably could have prevented the current ash shoots," says Queloz. The next threat is already identified: the beetle. He is still in the Belorussian region. But the propagation models show that it will be with us here 10 to 15 years.
The list of pathogens in the forest is growing longer and longer. The environmental change caused by climate change and globalization is to blame. More and more beetles, fungi and bacteria, which prefer a warm climate, find today a habitat in our latitudes. Every year, cantonal forest protection officers, foresters, gardeners, nurserymen and private individuals report 500 to 700 observations on the harmful species of beetles and fungi – and the trend is on the rise. "Local diseases are part of a healthy forest," explains Valentin Queloz. As long as the forest performs its functions, it is healthy. "And he does it."
(Tages-Anzeiger)
Date created: 29.07.2018, 23:15
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