Even dangerous stowaways can lurk in the caches of a load of lumber
The summary is made by artificial intelligence and checked by a human.
The bronze moth that lives in North America can wreak havoc on European birch species.
The mountain warbler and the pine woodpecker are potentially dangerous species for Finnish nature.
Pests are combated by maintaining forest diversity and favoring mixed trees.
SUomen’s forests have so far been spared extensive insect damage. Now Swedish researchers have warned that a beetle living in North America could destroy the birches of Northern Europe. Special expert of Natural Resources Center Heikki Noorteva investigates how pests threaten our nature.
Are Finnish birches in danger?
Special expert Heikki Nuorteva
In December 2023, Swedish researchers discovered that a beetle that lives in North America, the bronze moth, has wreaked havoc on European birch species.
For example, iron birches have suffered really badly. The Swedes assumed that the same could happen in Finland as well.
However, I personally don’t think that a bronze firecracker would cause complete destruction in our country. In Finland, you can find many other species of red moth, some of which also attack iron birch. The populations are kept under control with the help of predatory insects and parasites. I believe that the same species could limit the bronze lizard as well.
Which species would be the most dangerous?
One of the most potentially dangerous pests is the mountain weevil, a beetle found in Canada. It has not yet been observed in Europe at all.
The beetle uses only pine for food, which is about half of Finland’s trees.
Vuoristoniluri is hardy and could do well in Finnish conditions. The species hibernates as a larva, and in Canada it is estimated that the larva will only be destroyed by a continuous frost of at least forty degrees for a couple of weeks.
Another species that is dangerous when it spreads to us could be the pine roundworm, which is a microscopic nematode. It has destroyed large areas of forest in China and Japan. In North America, the species has adapted to the eel, so it has not caused much harm there.
The pine beetle does not itself move from one tree to another, but it moves with other insects, for example in the breathing tubes of the log ram. There are many species in Finland that the eel could use as a propagator.
How does an insect kill a tree?
Many species of insect pests cooperate with fungi. For example, the mountain woodpecker carries with it blue fungus, which contributes to the death of the pine.
When the fungus spreads in the wood, it blocks the wood’s transport routes and prevents fluid flows. Wood can dry out in just a few weeks.
In addition, the mountain nilur secretes very strong gathering pheromones, which attract more nilurs to the tree.
Similar pheromones are also secreted by the letterpress that haunts the moon, which is already found in Finland.
The mountain borer has caused extensive pine destruction in North America.
What is the situation in Finland now?
In recent years, forest destruction caused by insects has slightly increased. This is mainly due to the widespread use of letterpress printing. However, serious insect infestations have been isolated local cases.
The share of insect damage in all forest damage is very small here, only less than two percent. Snow, wind, moose and rotting fungi are responsible for the largest share.
In the rest of Europe, the insects have caused quite a bad effect in places. People from Central Europe have visited Finland to see why we have avoided more extensive insect damage.
How sensitive is our nature?
Lapland’s fell nature is quite sensitive. There, the larvae of the fell moth have killed the fell birches by eating them without leaves. So far, however, no extensive forest destruction caused by new insect species has been observed. The situation may change if a pest spreads here, which does well even in the harsh conditions of Lapland.
All in all, Finnish nature is surprisingly sustainable. After the ice age, we have developed quite a good diversity of species, and different insect and plant species have learned to balance each other. All in all, the trees have adapted to really harsh conditions and the natural insect predators and possibly the cold climate have kept the pest species under control.
There are also not very large forest areas in Finland where only one tree species grows. We have a lot of mixed forest that can resist insect pests that specialize in a certain tree species.
How to control pests?
It is best to keep the tree species structure and growth density of the forest favorable, favoring diversity and mixed trees.
Pests spread from one country to another in air currents or in wood and plant products. The Food Agency must start control measures if insects classified as quarantine pests by the EU are found somewhere. This could mean cutting down an entire forest.
For example, in Vantaa in 2015, harmful Asian hornet was found. To prevent the spread, deciduous trees had to be felled and disposed of in an area of several hectares. No other foreign species classified as quarantine pests have been found in our forests yet.
In the 1980s, pine ankeroi were found hiding in packing boards in the port of Turku. Timber imports from North America were temporarily suspended throughout Europe.
Live imported trees from areas where eels can occur need a phytosanitary certificate. Sawn timber and chips must be heated to 60 degrees before import. Even so, the creature has already reached Portugal and Spain in the EU.
Published in Tiede magazine 6/2024