2020

Spruce Bark Beetle Activity has Decreased Thanks to the Cool Weather

The Latvian State Forest Research Institute “Silava” carries our annual forest pest monitoring, which is part of the national forest monitoring. The cool weather this May was favourable for forest owners, as the activity of spruce bark beetles (Ips typographus) decreased significantly as compared to May 2019.

Data of the Latvian Centre for Environment, Geology and Meteorology show that this May the average air temperature was + 9.5oC, which is below the average monthly norm, thus May this year was the first since 1999, when the average air temperature was below + 10oC. The middle of May was the coldest period, when even a snow cover formed in the eastern part of the country, and the volume of precipitation in Latgale was almost two times above the norm.

The population of bark beetles had more than doubled in 2019 as compared to 2018. This was a serious concern for forest owners this year. Although the data of bark beetle monitoring carried out in May show that the activity of bark beetles has decreased, Edijs Leišavnieks, LVM Forest Protection and Fire Fighting Manager, urges forest owners to be vigilant, as the spruce pest must be paid attention throughout the summer.

“Only 10 – 15% of the bark beetle population can be influenced by the bark beetle's natural enemies; however, climatic conditions play a much more important role in the regulation of the bark beetle population. A wet spring or a relatively cold May can rapidly reduce the population of bark beetles and the reproduction of bark beetles can decline. However, wind gusts and dry summers promote the reproduction of bark beetles. Up to 70 thousand beetles can multiply in each cubic metre of wood cut down by wind that is not removed from the forest in time, which can destroy up to twenty trees in a forest stand,” tells Agnis Šmits, Leading Researcher at the Latvian State Forest Research Institute “Silava”.

However, the last week of May showed an increase in spruce bark beetle activity, with 80 – 90% of all beetles caught in May being trapped.  Currently, increased activity of bark beetles has been observed in LVM East Vidzeme region and in certain districts of LVM North Latgale regions. In order to minimize additional risk to healthy, undamaged spruce stands, guidelines for limiting spruce bark beetle damage have been updated by setting preventive and control measures in the most endangered forest areas.