Hundreds of insect species live on forest trees, but only a few dozen of them cause notable damage. Insects that feed on leaves or needles are mostly moths, sawflies, or leaf beetles. Bark beetles feed on the inner bark of trees and aphids on sap.

From the perspective of forestry, the insects that cause the most damage include large pine weevils, which feed on seedlings, pine sawflies, which abound especially in barren pine forests, and bark beetle species that specialise in spruce, such as the European spruce bark beetle and the spruce wood engraver.

Climate change may increase insect damage in forests

Erkki Oksanen
Photo: Erkki Oksanen, Luke

As the climate is warming, some pest insects, but not all, can become more prevalent and new species can spread to Finland. Damage caused by species that overwinter as eggs can increase in eastern and northern Finland.

Warmer summers and more frequent storms have already caused an increase in damage caused by spruce feeding bark beetles during this decade. The most effective means of preventing damage caused by bark beetles include removing damaged coniferous trees and softwood timber from stands before the next generation of beetles matures.

Research to promote practical forestry

The Natural Resources Institute Finland monitors the prevalence of the most important pest insects and studies the causes and consequences of insect damage. European spruce bark beetle inventories are carried out in collaboration with the Finnish Forest Centre. The Natural Resources Institute Finland also has research partnerships with various Finnish and international research organisations.

Photo on top of the page: Erkki Oksanen, Luke