The tone is scientifically cautious, but the message is highly alarming: “The high temperatures meant that the spruce bark beetles could no longer stand under the bark and began to swarm,” write the scientists from the State Institute for Forestry and Forestry (LWF). your current bark beetle newsletter on the Internet. “We are receiving reports of high numbers of bird printers arriving from numerous regions in Bavaria.” In the first week of April, more than a thousand beetles were caught in a number of traps that the LWF uses to monitor what is happening on the bark beetle front. In a few locations, especially in the Franconian Forest, there were even more than 3,000. Such values are usually reached at the beginning of May. That means: This year could be bad, very bad for many forest owners. Bark beetles are on the rise everywhere in Bavaria.
Forestry Minister Michaela Kaniber (CSU), who is responsible for combating the pest, is very worried. “I’m worried that our monitoring is already showing high beetle densities, especially in the north and east of Bavaria,” she says. “Caution is the order of the day. I urgently appeal to all forest owners to intensively check their spruce stocks in the spring.” Infected trees would have to be felled immediately and removed from the forests. You can recognize them by the drill dust at the base of the spruce trees that falls when the beetles bore into the tree. Kaniber also calls on forest owners to immediately repair broken snow from the previous winter and old storm damage in their forests, as they represent optimal conditions for the rapid spread of the pest.
The chairman of the Bavarian Forest Owners Association, Josef Ziegler, is also alarmed. “We have to expect that sooner or later the entire northeastern Bavarian low mountain range will be overrun by bark beetles,” he says. “Starting from the Franconian Forest, where there are already gigantic bare areas, through the Fichtelgebirge, the Steinwald and the Upper Palatinate Forest to the Bavarian Forest.” But forest owners should also be careful in the hilly areas south of the Danube, in the gravel plains around Munich and in the northern foothills of the Alps.
Clean-up work in a spruce forest near Munich that was damaged by broken snow and then by bark beetles.
(Photo: Florian Peljak)
The bark beetles, as printers and engravers are collectively called by forest owners and foresters all over the country, are probably the worst forest pests in this country. The two species of beetles, which are only a few millimeters tiny, attack the spruce, which, as the “bread tree of forestry”, as it is often called, is still by far the most common tree species in the forests of Bavaria. The beetles, which overwinter in the ground or in the wood, swarm out in spring when temperatures reach around 16 degrees.
Then they bore into their host trees, create tunnels between the bark and wood, mate and the females lay the fertilized eggs. After one to two weeks, the larvae hatch and eat their way through the sap-bearing layer of the spruce trees. It takes seven to twelve weeks for the new generation of beetles to fully develop. The pests get their name from the damage they leave behind in the infected spruce trees. The printer’s is vaguely reminiscent of an open book page, the engraver’s is similar to an engraving.
Bark beetles benefit from climate change; the earlier it gets warmer in the year, the earlier they start to swarm. And the longer it is mild in autumn, the longer they are active. They also cope well with the increasingly mild winters. In the past, bark beetles typically produced one to two generations of offspring per year. As the climate crisis progresses rapidly, three-generation years are becoming more common.
Such mass proliferation is the nightmare of every forest owner and forester. “With three generations per year, a single female printer can have 100,000 offspring,” says forest protection specialist at the Forestry Ministry, Franz Paulus. “No spruce forest can withstand such gigantic reproduction rates.” 2023 was a year with three generations of bark beetles. That doesn’t bode well for this year either. “There is a large beetle population waiting in the wings,” says the LWF scientists’ newsletter.
Especially since the bark beetle has spread rapidly in Bavaria in recent years. Worst at the northern end of the Free State in the Franconian Forest. The images from there are similar to those known from the Harz, the Saxon Elbe Sandstone Mountains and other forest disaster regions in Germany. Last autumn, the bare areas in the Franconian Forest alone, i.e. the former forests on which there are no longer any trees because of the pest, amounted to more than 7,000 hectares. This is equivalent to 10,000 football fields and accounts for 15 percent of the region’s total forest. Even beyond the Franconian Forest, no Bavarian forest owner can feel safe. This is shown by a look at the bark beetle threat maps that the LWF scientists publish every year for the Bavarian forestry administration. They vividly show how the pest threat has spread across Bavaria in the last four years.
The danger of bark beetles has increased massively everywhere in Bavaria in recent years.
(Photo: SZ-Grafik)
It is therefore not surprising that the damage is also at a record level. In 2023, Paulus and his colleagues counted 6.3 million cubic meters of beetle wood across Bavaria. That’s an incredible amount: it could be used to build a three meter high and one meter thick wooden wall from Gothenburg in Sweden to Palermo in Sicily. And the statistics show something else: The damage has been increasing for a good 30 years, not linearly, but in a kind of wave movement, but the bottom line is very clear – from a good four million cubic meters of beetle wood in 1993, 1994 and 2005 to more than five million cubic meters in 2018 and most recently to 6.3 million cubic meters in 2023.
As far as the future is concerned, forest owner boss Ziegler is also pessimistic. He expects that beetle wood will soon exceed the ten million cubic meter mark. According to his prediction, in the next 25 to 30 years, half of the spruce trees currently in the Bavarian forests will fall victim to the pest. “If we add everything up, we currently have around 500 million cubic meters of spruce wood supplies in the Free State,” says Ziegler, who has been at the head of the Bavarian Forest Owners Association for eight years and will soon be retiring from the office. “We will lose 250 to 300 million cubic meters of this to the bark beetle.” Ziegler also has a sum ready for the financial loss that this will cause to the Free State, the municipalities and the many thousands of private forest owners in Bavaria: ten billion euros.
The only hope that forest owners and foresters have left for this year: that it won’t be as warm as it seems. But rather cool and rainy. Because the bark beetles don’t like that. Then they don’t multiply as much and don’t spread as much.