Bark beetle - the most dangerous forest pest that causes huge losses to forest owners!

What is a bark beetle?

Bark beetles are named as such because they reproduce in the inner bark of trees, in living and dead phloem tissues. Adult beetles overwinter in forest litter and infected trees when environmental conditions are not favorable for reproduction. In spring, when warmer weather begins (usually in May), bark beetles start to travel (can travel up to 1km) in search of weakened trees. When a tree is found, the bark beetle burrows through the weakened bark to create tunnels where it can mate and lay eggs. Bark beetles are especially dangerous because the release of pheromones attracts large numbers of other bark beetles, resulting in attacks on healthy trees and thus destroying entire tree stands over large areas. If weather conditions are favorable (warm and dry weather), the bark beetle can migrate to the next tree two to five weeks after tree infection and repeat the process. Under favorable conditions, up to three generations of bark beetles can be created. When the larvae hatch, they feed and pupate under the bark.

Bark beetles communicate with each other using semiochemicals, compounds or mixtures that carry messages to other members of the species. Some electrophysiological and behavioral statistics suggest that bark beetles can sense not only olfactory signals directly from other bark beetles, but also some compounds from trees. They are also believed to be attracted to ethanol, which is one of the by-products of microbial growth in dead wood tissues.

How to fight bark beetles?

If we look specifically at the Latvian context, a big problem is irresponsible forest management, because bark beetle outbreaks are promoted by neglected spruce stands where timely young stand maintenance has not been carried out and tending felling has not been performed. When spruces grow too densely, they become elongated, resulting in a small and weak root system, which means that spruces are easily damaged by wind, which in turn attracts bark beetles. It is also recommended to plant spruces in mixed stands with birch, as these species get along well and promote better stand formation, with birch protecting spruces during storm periods.

The next significant factor that has contributed to the spread of bark beetles is the untimely response to the spread of bark beetles. At the state level, a plan should have been developed to inspect forest stands, and when bark beetle presence is noticed, simplified and accelerated forest felling should be applied in the specific property or region. It was already clear in 2017 that due to the bark beetle invasion in Europe (Europe suffered 25% of spruce stands from 2017 to 2022), Latvia would face a similar fate and an action plan should have been developed, which unfortunately was not done. As German experience shows (40 million m3 felled additionally due to bark beetles), lightning-fast action is needed, sick trees must be felled and up to a kilometer along the perimeter around the affected stand, to limit the spread of bark beetles.

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What is the situation in Latvia?

Now is the last moment to act, the infected areas must be identified urgently so that it is possible to cut down as many damaged and surrounding stands as possible this winter. To make bark beetle control measures effective, felling must only be carried out in winter, while the bark beetle is dormant, and it is also mandatory to remove branches from the felled stands.

Timbro calls on everyone to treat the bark beetle invasion responsibly and manage their forests wisely, because the neighbor's forest is next to yours. Only by acting in a timely manner and helping each other as responsible owners and comrades can we protect our and the surrounding forests from this bark beetle invasion, so that the expensive spruce sawlog does not turn into firewood!