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Doris Hölling

Forschungsanstalt WSL

Swiss Federal Research Institute WSL
Swiss Forest Protection
Zürcherstrasse 111
CH - 8903 Birmensdorf

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Fax: +41 44 739 22 15


Author(s): Doris Hölling
Editorial office: WSL, Switzerland
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The Asian longhorned beetle in Europe

This particularly dangerous quarantine pest was first spotted on European sites in 2001. Infestation sites have been on the rise since.

ALB-Freilandbefall in Europa
Fig. 1 - The map shows the known instances of outdoor ALB infestations in Europe to date. Red: Areas that are still under monitoring. Green: Areas which have been successfully eradicated. Click to enlarge.
Fig. 2 - Crates loaded with granite blocks.

Photo: Doris Hölling (WSL)

Fig. 3 - Maple (depicted), willow, birch and horse chestnut trees are the most common host trees.

Photo: Doris Hölling (WSL)

This invasive species of beetle enters Europe within wooden packaging, primarily wooden pallets and crates used as packaging for granite from China. Although the beetles can only lay their eggs in living wood, their larvae can develop within wooden slats.

Correct heat treatment of wooden packaging would prevent beetles from developing during shipping or when in the destination country. Unfortunately, the corresponding markings are often just stamped on imported goods, with the packaging having undergone inadequate heat treatment, if any.

The non-native Asian longhorned beetle (ALB) infests different types of native hardwood trees (even healthy ones) and can cause dieback within just a few years.

Consistent control is needed

Sightings of the Asian longhorned beetle must be reported and consistently controlled. All instances in Europe are reported to the European and Mediterranean Plant Protection Organization (EPPO), which has served as the central hub for European cooperation (among 50 countries) on European and Mediterranean plant protection since 1951.

All information in this article regarding outdoor infestations is based on EPPO reports.

15 outdoor infestation sites in Europe have been eradicated to date, three are unclear. All others are still being monitored.

An infestation is only considered to have been eradicated once at least two successive generations have passed at a given site without any additional reported sightings of the pest or symptoms of its infestation. This period may be extended to three infestation-free generations in areas where development cycles are prolonged owing to the short vegetation period or where development time is variable.

Visual monitoring is carried out by specially trained tree climbers who are supported by specialist sniffer-dog teams at some infestation sites. Scientists identify the beetles, larvae, pupae or eggs, as well as the noted symptoms. In addition, a DNA analysis is sometimes conducted to unequivocally confirm the identity of the pest.

Infestation sites in Europe


All Austrian infestation sites are from Upper Austria:

The Asian longhorned beetle was sighted for the first time in Europe at Braunau am Inn (close to the German border) in July 2001. It took 12 years to eradicate this infestation (completed in 2013).

However, another outbreak was reported 2013 in Gallspach, which is also located in Upper Austria. The area is still under monitoring.

In 2012, a new record came from St. Georgen/Geinberg (located along the Inn river), where an exit hole and three trees infested with living larvae were found. The infestation has been considered to be eradicated since late 2016.

Auswurf von Spänen am Stammfuss
Fig. 4 - Numerous dislodged chips of bark at the foot of an infested tree. Both the large number of chips and the various old exit holes indicate an older infestation.

Photo: Beat Forster (WSL)

gelagerte Paletten
Fig. 5 - The quarantine pest arrives in Europe via wooden packaging. Some of the beetles hatch in the container in transit. The pest can also mature fully in stored waste wood and fly away.

Photo: Doris Hölling (WSL)

In France, this invasive beetle species first appeared in 2003. It is now known to occur in five regions. One infestation is considered to be eradicated.

Centre-Val de Loire region:
A relatively old infestation comprising many beetles, pupae and larvae was discovered in Gien industrial park. Beetles and infested trees were also reported in this area between  2004 and 2008, and symptoms of infestation were spotted again in 2016. Between November 2016 and October 2018 102 infected trees were found.

Pays de la Loire region:
Beetles were discovered in Saint-Anne-sur-Brivet in 2004, where numerous larvae, beetles and eggs as well as over 77 infested trees continued to be found until 2005. Only one beetle was found in 2006. This infestation is considered eradicated since 2013.

Alsace-Champagne-Ardenne-Lorraine region:
A beetle and two infested poplars were discovered at the port of Strasbourg in 2008. A survey unearthed several hundred larvae and eggs as well as dead beetles and pupae. Exit holes were spotted on three maple trees in 2010. In addition, larvae of varying ages and mature pupae were found inside the trunk. It is assumed that this infestation  began in 2003 and remained undetected for two generations. The pests are believed to have come here in the packaging of granite from China. Since April 2019, this infestation has been deemed to have been eradicated.

Corsica region:
In July 2013, two homeowners in Furiani reported numerous beetles and symptoms of an ALB infestation. Phytosanitary inspectors found additional infested trees with egg-laying sites and 60 beetles on the same day. Numerous companies that use wooden packaging are located in the vicinity of the infestation site.No symptoms were detected in 2018 and 2019.

Auvergne-Rhône-Alpes region:
In late summer 2016, a Divonne-Les-Bains resident reported another ALB infestation. Many maples were infested. Living beetles and numerous larvae, as well as egg-laying sites and different old exit holes were also found in the town. In 2017 an infested maple was discovered, in 2018 4 infested maples and in 2019 8 infested trees (4 maples, 2 willows, 2 horse chestnuts).

Fig. 6 - Infected trees on the roadside in Schönebach (Bavaria); a exit hole in a roadside tree (upper right photo).

Photo: Doris Hölling (WSL)

ALB mit weisser Fleckung
Fig. 7 - Most Asian longhorned beetles found in Europe have white markings, as depicted here.

Photo: Doris Hölling (WSL)

Bayerischer ALB mit anderer Farbverteilung
Fig. 8 - An ALB with slightly unusal markings was found in Bavaria. Unlike the individual markings found on the other beetles, the borders  between markings were not indistinguishable.

Photo: Doris Hölling (WSL)

Asian longhorned beetles were first sighted outdoors in Germany in 2004. Sightings of the quarantine pest have now been reported in four federal states. One infestation site has been eradicated to date.

In 2004, all development stages and symptoms were spotted in Neukirchen am Inn. The intensive monitoring led to the fact that the infestation has been deemed to have been eradicated since the end of 2015.
Since then, this species of beetle has also been seen outdoors in the greater Munich area: in Feldkirchen in 2012 and in Neubiberg in 2014/2015. In 2014, the invasive beetle species was additionally sighted close to Augsburg in the Schönebach area of Ziemetshausen. Some trees were heavily infested. In April 2016 a plant inspector reported an ALB infestation in the Kelheim port area. This is a major outdoor infestation affecting 18 maple trees; some of their branches were already dead when the infestation was reported. It is assumed that the beetles came to the area in wooden packaging. Pheromone traps are used there, among other things.

A new outdoor infestation was sighted in October 2016 in Murnau. Plant inspectors reported symptoms on 19 trees (maples and chestnut trees) in public and private green spaces and along a railroad track. This involved recent and old exit holes, eggs, and brittle branches and crowns. The 2017 monitoring will include visual control as well as pheromone traps, trap trees and sniffer dogs.

At the beginning of August 2019 an infestation with ALB was detected in Miesbach. More than 30 beetles were caught.

North Rhine-Westphalia:

In Mönchengladbach, a beetle on a maple tree from a private garden was reported in 2004. Apparently no population could establish itself.

Another outdoor infestation was spotted in 2005 in Bornheim in the immediate vicinity of a granite importer. An additional infestation involving three heavily infested maples was discovered in Alfter in 2009.

Reports of the quarantine pest have also come from the port area of Weil am Rhein since 2012.
In early summer 2015, sniffer dogs in Grenzach-Wyhlen found two empty egg shells, as well as a larva in its early stages of development, during routine checks of the district administration office. As the monitored areas of both infestation sites fall partly within Switzerland, the infestations are also monitored there. Since the beginning of 2019, both areas have been considered extinct.

In early August 2016, a homeowner in Hildrizhausen (Böblingen district) found a beetle in his garden. A search (with sniffer dogs) was launched immediately, and the team found a further 14 beetles and eight infested trees. Another beetle was spotted shortly afterwards, this time in Altdorf (also in the Böblingen district). However, the search there for exit holes, other symptoms of infestation or additional beetles was inconclusive. This beetle may have been brought there in firewood or by a vehicle.

A bigger ALB infestation was discovered in Magdeburg in 2014. In 2015, sniffer dogs were used there. In 2016, 50 trap trees and 200 pheromone traps were used; these caught another eight beetles.


The Asian longhorned beetle first appeared in Italy in 2007. It was later found in three other regions.

In June 2007, the invasive beetle species was discovered in a private garden in Corbetta, where a maple tree and three birches showed signs of infestation.
Two infested maple trees were spotted in Vittuone in March 2010, though no signs of infestation were recorded in 2011 or 2012.

Two infested maple trees were reported in Sedriano in 2013. It is assumed that the infestation was connected to a company that worked with packaging and had previously been located in the area.

Veneto region:
An infested maple tree was spotted in a garden in Cornuda in 2009.
An infested group of trees was discovered in Maser in 2010.

In 2017 and 2018 no infested plants were discovered.

Marche region:
Exit holes and egg-laying sites were discovered on a maple tree in a private garden in Grottazzolina in August 2013.

In 2019 two new infestations were reported from the Marche region.
Fermo, Province Fermo: beetles and symptoms were found in maple and elm.
Civitanova, Province Macerata: 6 infected maples, 3 infected horse chestnut trees and 1 infected poplar and 1 infected elm each as well as adult beetles.

Piedmont region:
In 2018, two new outdoor infestations were discovered in Piedmont:
In July, in Vaie (province of Turin), two infested maple trees were spotted in an urban park, 34 maples along a road, as well as one willow. Beetles, larvae, eggs and excursion holes were found on the two 12-metre-high park trees, and mainly egg deposits on the other, smaller trees. Phytosanitary measures were implemented immediately. Insecticides were also used.

In September 2018, 87 infested maple trees, 3 birchand 1 horse chestnut were discovered in Cuneo (province of Cuneo). Here, too, phytosanitary measures were taken immediately. In both cases, the path of introduction is unknown.


In 2008 2 beetles were found in a private garden. Probably they were brought in with packaging wood from Chinese stone goods. Since 2011 this infestation is considered to have been eradicated.

The Netherlands

Sightings of the Asian longhorned beetle have been reported in two Dutch provinces. Both infestations have now been eradicated.

Province of Flevoland:
The first outbreak of this pest in the Netherlands was discovered in Almere in 2010, which was an unusual infestation owing to the fact that both living and dead beetles as well as larvae were found in an industrial park, but there were no eggs. Some exit holes were presumably around three years old by the time they were detected. The infestation has been eradicated in 2011.

Gelderland province:
Another infestation site was discovered in 2012 in Winterswijk and some of the exit holes there were also three years old. Four years later (2016), this infestation has been reported as eradicated.

Asiatischer Laubholzbockkäfer mit gelblicher Zeichnung
Fig. 9 - Marly (Switzerland) is the only site in Europe where beetles with yellow markings were discovered alongside beetles with the usual white ones. You can find additiona information about the Asian longhorned beetle on the WSL’s information sheet (in German).

Photo: Doris Hölling (WSL)

Käfer mit nur spärlicher weisser Fleckung
Fig. 10 -  Some of the beetles in Berikon have somewhat sparse markings and appear almost black when first seen.

Photo: Doris Hölling (WSL)

Sightings of ALBs have been reported in three Swiss cantons. Three infestation sites have been eradicated. In the meantime, all infestations have been eradicated in minimal time.

Canton of Fribourg:
Switzerland’s first outbreak was recorded in 2011 in Brünisried. This site was peculiar, owing to the fact that no exit holes were found despite intensive searching. It came to light in 2014 that this outdoor infestation was caused by the shipment of infested firewood from Marly (Fribourg), which was only discovered in 2014.
This discovery made it clear that, in addition to checking potentially infested trees, stores of firewood should be monitored.
At the Brünisried site, it emerged that, owing to the relatively high altitude and the associated shorter vegetation period, the ALB's development cycle could last three years, resulting in dissipated development.
In 2012, neither beetles nor symptoms were found in Brünisried. However, in 2013, beetles, larvae and exit holes were spotted once again. At that point, similar control measures to those used in the infested area in Winterthur were implemented. After four infestation-free years, the outdoor infestation in Brünisried – Switzerland's first – has been considered eradicated since late 2017.

The large infestation site in Marly with two focus zones has also been considered to be eradicated since late 2018 - in a minimum time of only four years.

Canton of Zurich:
An outdoor beetle infestation was discovered in 2012 in Winterthur. A row of maples was infested, as were numerous trees from the nearby industrial park and residential area. Around 140 exiting beetles were spotted, as were many larvae, pupae, egg-laying sites, exit holes and signs of maturation feeding. Most of the exiting beetles at both Marly and Winterthur could be caught upon discovery of the infestation. The Marly infestation was unusual in that most of the beetles had yellow markings. This is the only time to date that this marking pattern has been spotted in Europe.
Since winter 2016, after four years without infestation, one infestation site is considered to be eradicted. This shows that it is quite possible to eradicate even a large infestation within four years.

Canton of Aargau:
A further outdoor infestation was reported in Berikon in September 2015. Once again, most of the beetles sighted were flying out from a maple tree. Some of the beetles had somewhat sparse markings, so at first sight they appeared almost black. This field infestation could also be reported as eradicated in the minimum time of 4 years at the end of 2019.


The quarantine pest was sighted for the first time in the UK in 2011 close to Paddock Wood, Kent, where over 200 living larvae were discovered. Since 2019, this field infestation has been deemed to have been eradicated.


Finland’s first outdoor infestation of ALBs was spotted in October 2015, when two beetles were found on the pavement by an employee of a stone importing company in Vantaa, close to Helsinki. Further investigations carried out in the surrounding area identified suspicious signs, such as egg-laying sites in birch and willow trees. Once these trees had been felled, larvae and one beetle that was ready to hatch could be seen. It is assumed that the quarantine pest arrived at the company’s site in wooden packaging. Investigation at this site included visual inspections, sniffer dogs and pheromone traps.


The first outdoor infestation was spotted in October 2015, on a willow in  Budva. Its origin is unknown. Control measures were taken immediately and have remained negative so far. 


In 2003 an infestation of a private bonsai was reported from Poland. However, this report is unclear.



An ALB infestation was also reported from the city of Aabrine in northern Lebanon. Two beetles were discovered there in 2015, another animal in 2016. It is possible that the introduction took place with packaging wood material.

For further information: