France has put in place a four-part national plan in a bid to combat an insect that destroys trees and is so invasive that by the time the insect is visible on the tree it is already too late to save.
The bark beetle works “strategically”, say experts. The insect lands on the tree and sends out pheromones to warn other insects. The male and female penetrate under the bark and mate. The female then makes a tunnel, lays her eggs and leaves.
Larvae then emerge from the eggs, and create more channels by eating into the wood, towards the centre of the tree. This behaviour leads to the death of the tree.
Later, the larvae become insects themselves, and infect other trees.
The bark beetle is already common in Canada and Germany and is now spreading in France, partly due to increases in temperatures, episodes of drought and heat waves.
There are around 140 species of beetle in France, of which 10 are considered to be damaging to forests, states animal specialist magazine Le Mag des Animaux.
Bark beetles are small, measuring between 2-7 mm. They generally have a compact, cylindrical body in shades of brown to black, with antennae, and six legs adapted for digging and moving through wood. They are usually attracted to the smell of dead or freshly-cut wood, but if there is not enough of this they will attack living trees.
Millions of square metres damaged
The Agriculture Ministry has said that French coniferous forests have suffered significant damage caused by bark beetles since 2018, and estimated that wood in crisis in the “north-eastern quarter of France has reached 37 million m3 (22 million m3 of spruce and 15 million m3 of fir)”.
It also said that 110,000 hectares have been damaged, of the 520,000 hectares of spruce and fir in the affected regions.
“This considerable damage not only has an impact on landscapes and ecosystems, but also on the supply of wood to companies in the sector, in terms of volume and quality, as well as on future wood availability,” it said.
Four-part forest plan
The ministry is continuing the ‘Plan national d'actions Scolytes et Bois de crise (national action plan on bark beetles and crisis wood)’, which was launched in 2024 in a bid to support the forestry sector.
The plan has four main focuses.
Forestry groups have been tasked with better anticipating crises and their consequences. The aim is to improve the storage and processing of wood, along with educating communities on the matter.
An aid scheme covering 65% of the cost of these kits was launched in April 2024. Forestry professionals use these kits to help their trees when the woods are infested. ‘Debarking’ trees is currently considered the most effective method of combating bark beetles. The plan closed in summer that year.
The supply areas for biomass power plants that have received public funding are to be expanded, in a bid to prioritise the use of damaged wood from crisis areas. The scheme works in partnership with the French environment and energy management agency ADEME.
Regional prefects are responsible for issuing decrees to the municipalities affected by this expansion. So far, this has applied to communes in the regions of Auvergne-Rhône-Alpes, Bourgogne-Franche-Comté, and Grand Est.
Forests are set to receive a 20% increase in aid to promote their renewal under the France Nation Verte programme. Trees damaged by bark beetles are considered to have been “damaged by a biotic phenomenon (such as a pest or pathogen)”, and defined as “crisis wood” eligible for aid.
Tree training
Workers from the national forestry office, l’Office National des Forêts are now trained to identify infested trees. These are then cut down and removed as quickly as possible, with the wood taken to a sawmill where it is immersed in water or debarked, so the insects cannot complete their cycle.
The forest health department le Département de la Santé des Forêts has also begun to install traps with pheromones, which attract females and prevent the beetles from attacking the trees.
Beetle brings a fungus that contributes to deterioration of trees
Michel de Kerleau, from near Loudéac (Côtes-d'Armor, Brittany), who manages a school orchard, told newspaper Actu.fr that he had discovered several of his trees in a poor state, and found the beetle to be the culprit.
He added that the beetle had also brought a fungus that “occupied the tree’s vessels” and contributed to its deterioration even further.
Read also: Crisis unit set up as parasite ravages pine trees in south of France
How can I tell if my trees are affected?
Trees ravaged by bark beetles tend to show several signs:
Deposits of sawdust on the trunk and at the base
Some dried-out twigs and branches
Lifting bark in some places
Small holes in the bark, and evidence of tunnels (see photo above)
Fir needles turn brown before falling
Hardwoods turning black due to fungi in the tunnels
Trees that are affected should be felled immediately, submerged in water, debarked, or burned (e.g. in a wood burning stove) to avoid the beetles spreading to more trees.
