Rain hardly impedes the progress of the bark beetle.

Nature - Rain hardly impedes the progress of the bark beetle.

A brief pause in the invasions: The recent colder, wetter weeks have temporarily slowed down the upcoming pine beetle infestation in the Baden-Württemberg coniferous forests. Moderate temperatures and persistent rainfall have led to a slight decrease in catches in monitoring traps in Baden-Württemberg and Rhineland-Palatinate, according to Markus Kautz from the Forest Protection Department of the Forest Research and Experimental Station (FVA) in Freiburg. However, there are still four-digit catch numbers reported.

Hotter summer temperatures will soon bring a surge of bark beetles and cause new infestations, warned Kautz. "The rain didn't make a difference, it's not a game-changer," he said. The beetle population is currently high at many locations.

Specialists at the FVA are worried as these bark beetles, who mostly target spruce, have been active since April due to the warm temperatures. Even though there was a temperature drop during the changeable April weather, the already laid eggs didn't die off. "The threat of infestation is likely to continue growing," explained Kautz.

It's expected that the early swarming season might become a norm due to climate change. The start of the swarming may shift towards March, meaning the pine beetle will be active for longer and can affect more drought-affected trees. Through this extended phase, pine beetles also have enough time to breed a third generation which is increasingly common. This will lead to more of them surviving the winter and attacking increasingly weakened trees.

Hotspots of infestation are reported in the southern Black Forest, Odenwald, and parts of the Hunsrück. The FVA notes a gradual shift towards the north. While there are still the highest damage numbers in the south, an infestation is now expected to occur more frequently in the Middle and Northern Black Forest. The reason: The spruce population in the south has become scarce due to the long-term infestation. "As soon as the spruce shares drop below a certain level, the pine beetles advance in steps," said Kautz. However, in the Middle Black Forest, there's mainly privately-owned forest, which is difficult to observe and can only be protected at great cost.

"We also hear from our businesses that they are dealing with live infestations and the beetles are moving into fresh trees," said the Forest Chamber Baden-Württemberg's managing director Jerg Hilt. He called for more political support, but also expressed frustration: "Private and municipal forest owners cannot handle this alone. It's a tragedy that there are no signals from the federal government," he stressed. The federal government has ended the five-year special funding at the end of the year - funds used for reforestation, storing damaged wood, and hunting for pine beetles. "This is a dangerous signal for many forest owners and not encouraging. It's about time."

Summer days are ideal for the bark beetle: The warmer and dryer the days, the faster the beetles reproduce. They bore into the trees and lay their eggs under the bark. After hatching, the larvae feed on the bark layer of the tree. This thin layer under the bark is the vital vascular system of the tree. If this layer is destroyed, the tree dies. Two hundred bark beetles can damage a single tree so much that it cannot survive.

Therefore, infected trees must be removed from the forest as soon as possible to avoid further damage. They can go directly to dry or wet storage or directly to sawmills. "You can't fully control it, and the damage is limited," says Kautz. "They're constantly catching up."

FVA's plans for wiping out pine beetles by 2024

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Read also:

1. In an attempt to combat the bark beetle infestation, researchers in Fribourg, Switzerland, are studying the role of insects in forest ecosystems, hoping to find natural predators to control the population.
2. The recent rainfall has not significantly impacted the bark beetle infestation in the southern Black Forest, as reported by forestry officials in Baden-Württemberg and Rhineland-Palatinate.
3. In response to the ongoing bark beetle infestation, authorities in Fribourg have implemented measures to protect vulnerable trees, including the application of pesticides and the removal of dead or weakened trees.
4. A team of researchers in Baden-Württemberg's Forest Research and Experimental Station (FVA) in Stuttgart is working on developing new methods for controlling the bark beetle population, such as using certain fungi to kill the beetles.
5. In an effort to take a breather from the constant threat of bark beetle infestations, some forest owners in Baden-Württemberg and Rhineland-Palatinate are turning to afforestation projects, planting new trees to replenish damaged forests.
6. Despite the challenges posed by the bark beetle infestations, environmental organizations in Fribourg, Baden-Württemberg, and Rhineland-Palatinate are advocating for sustainable forestry practices that promote the health of the forest ecosystem and support the natural predators of bark beetles.

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