Citrus Long-Horned Beetle: An Emerging Threat to Hazelnut Orchards

What Is the Citrus Long-Horned Beetle?

The citrus long-horned beetle (Anoplophora chinensis) is an invasive insect species native to East Asia. Belonging to the longhorn beetle family (Cerambycidae), this pest feeds on the cambium and heartwood of broadleaf trees, often killing the host tree in the process.

First detected in Turkey in 2014 in Istanbul, the pest spread to hazelnut orchards in the Macka district of Trabzon in 2018, posing a major threat. In infested hazelnut orchards, it has caused yield losses of up to 50% and the complete dieback of hazelnut bushes.

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A Serious Threat

Unlike native pests, the citrus long-horned beetle does not merely reduce yield — it causes the complete death of hazelnut trees. It destroys the trunk and root system of its host tree, inflicting irreversible damage.

Identification Features

Adult Beetle

Size: 20-35 mm in length, robust build
Colour: Glossy black body with white spots
Antennae: 1.5-2 times the body length, with black-blue bands
Legs: Blue-black in colour
Sexual dimorphism: Males have antennae longer than the body; in females, the antennae are approximately body length

Larva

Size: Reaches 40-50 mm at maturity
Colour: Creamy white, legless
Head: Brown, equipped with powerful mandibles
Habitat: Inside tunnels bored in the trunk and thick branches

Egg

Size: Approximately 5-7 mm
Colour: Creamy white, oval
Oviposition site: Beneath the bark, in a “T”-shaped slit carved by the female’s mandibles

Life Cycle

The citrus long-horned beetle has a 1-2 year life cycle. The time required to complete one generation varies depending on climatic conditions.

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Seasonal Overview

September - April: Larval and pupal stage (inside the tree) May - August: Adult stage (flight, mating, oviposition)

Egg Stage (Summer)

The female carves a T-shaped slit in the bark with her mandibles and deposits one egg per slit. A single female can lay 70-200 eggs in her lifetime. Eggs are typically deposited on the trunk up to 30-40 cm above ground level.

Larval Stage (Autumn - Spring)

After hatching, the larva initially feeds beneath the bark, then bores into the woody tissue. It excavates wide tunnels through the cambium layer and heartwood. These tunnels sever the tree’s nutrient and water transport systems, eventually causing the tree to die.

Pupal Stage (Spring)

The mature larva forms a pupal chamber at the end of its tunnel inside the tree. The pupal stage lasts 2-4 weeks.

Adult Stage (May - August)

The adult beetle emerges by boring a round exit hole 8-12 mm in diameter through the trunk. Adult lifespan is approximately 1-2 months, during which mating and egg-laying occur. Adults have a flight range of 500 metres to 2 km, enabling the pest to spread to neighbouring orchards.

Damage Symptoms in Hazelnut Orchards

Symptoms on the Trunk

Exit holes: Round holes 8-12 mm in diameter on the trunk (the most conspicuous sign)
Frass accumulation: Sawdust-like wood frass at the base of the trunk and around exit holes
Bark lifting: Bark swelling caused by oviposition slits
Sap exudation: Sticky sap oozing from the trunk

Symptoms Across the Tree

Leaf wilting: Yellowing and wilting at branch tips
Branch dieback: Branches severed by larval tunnels die back suddenly
Crown thinning: Progressive leaf loss in the upper canopy
Stunted shoots: New shoots remaining shorter than normal
Tree death: Complete dieback of the tree at advanced stages

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Early Detection Is Vital

If you observe exit holes or frass accumulation on the trunk, immediately notify your Provincial or District Directorate of Agriculture and Forestry. Early detection is the single most critical step in preventing the pest from spreading.

The Spread in Turkey

First Detection: Istanbul (2014)

The citrus long-horned beetle was first recorded in Turkey on 12 June 2014 at the Kumbaba Nursery in the Sile district of Istanbul. It was found on maple and willow trees, and a control regulation was published in the Official Gazette on 17 June 2014.

Spread to Hazelnut Orchards: Trabzon (2018)

The pest appeared in hazelnut orchards in the Esiroglu neighbourhood of the Macka district of Trabzon in 2018. Research indicates that the beetle was introduced to the region between 2016-2017 via infested nursery stock transferred from an Istanbul Metropolitan Municipality nursery to a Trabzon Metropolitan Municipality nursery. Because this nursery was located within the Macka/Esiroglu neighbourhood, the pest readily spread to surrounding hazelnut orchards.

Control Campaign (2018-2021)

Period	Intervention	Outcome
2018-2020	Chemical control	Proved insufficient; spread continued
Winter 2020	Removal of infested orchards began	Effective but initiated late
April 2021	Control area reached 3,600 decares	Removal 99% complete (official statement)

Affected Area

Satellite imagery and remote sensing analysis determined that the total area of hazelnut orchards destroyed was 2,296.6 decares. Affected neighbourhoods:

Macka District: Gunay, Esiroglu, Barisli, Hizarli, Alacam, Yenikoy Ortahisar District: Caglayan

The greatest damage occurred in the Esiroglu and Gunay neighbourhoods.

Control Methods

Eradication (Removal)

According to the official control regulation, the most effective method is the complete destruction of infested plant material:

Infested trees are uprooted and burned
No new hazelnut trees are planted in cleared areas for at least 2 years
Removal should be carried out during the winter period (larval and pupal stage)

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No Alternative to Eradication

Because the larva lives deep inside the heartwood, reaching it with insecticide application is virtually impossible. For this reason, the uprooting and destruction of infested trees is the most reliable control method.

Quarantine and Buffer Zone

Under the Official Gazette regulation, a buffer zone at least 2 km wide must be established around destroyed hazelnut orchards:

Orchards within the buffer zone are inspected twice a year
Inspections aim to detect the pest’s presence at an early stage
The buffer zone established in Trabzon covers an area of 13,687.4 decares

Nursery Stock Control

The transport of infested nursery stock is the greatest risk factor in the pest’s spread:

Saplings from within the buffer zone must not be used to establish new orchards
A phytosanitary certificate should be required for all sapling transfers
Suspect nurseries must be inspected regularly

Chemical Control (Limited Effectiveness)

Chemical control alone is insufficient, but it can serve as a supplementary measure during the adult stage:

Adult stage: Trunk-directed spraying between May and August
Trunk painting: Lime and insecticide mixture applied to the lower trunk
Systemic insecticides: Application by trunk injection (limited success)

Mechanical Control

Wire probing: A thin wire is inserted into larval tunnels to kill larvae mechanically
Adult collection: Adults observed on trunks during the adult stage are collected by hand and destroyed
Trap trees: Attractive tree species are planted to lure beetles away from hazelnut trees

How to Inspect Your Orchard

Growers with hazelnut orchards in the buffer zone or in at-risk areas should carry out regular inspections:

When to Inspect

During winter basal shoot clearing, inspect the trunks
Between May and August, monitor for adult beetles

Inspection Checklist

Examine the trunk from ground level up to 30 cm above the soil line
Look for round holes (8-12 mm diameter)
Check for frass deposits at the base of the trunk
Search for T-shaped slits or raised areas on the bark
Note any sudden branch dieback or leaf wilting

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Mandatory Reporting

The citrus long-horned beetle holds quarantine pest status. If you detect any suspicious signs, immediately notify your Provincial or District Directorate of Agriculture and Forestry. Prompt reporting is the most important step in bringing the pest under control.

At-Risk Regions

The citrus long-horned beetle currently has no officially recorded infestations outside Trabzon province. However, the following factors increase the risk:

Unregulated nursery trade: The possibility of infested saplings being transported to other provinces
Wide host range: Not limited to hazelnut alone; the beetle can survive on maple, willow, beech, poplar and many other broadleaf tree species
Climate tolerance: Its broad climate tolerance increases its capacity to adapt to different regions
Forest connectivity: Coppice forests surrounding hazelnut orchards can serve as alternative habitats, allowing the pest to persist

Conclusion

The citrus long-horned beetle poses a far greater threat to Turkish hazelnut farming than any native pest. This invasive species, which kills its host tree, has led to the destruction of thousands of decares of hazelnut orchards in the Macka district of Trabzon.

Keys to successful control:

Early detection is the most critical step — inspect your orchard regularly
If you find suspicious signs, report immediately to the agricultural directorate
Never purchase unregulated nursery stock
If you are within the buffer zone, carry out detailed inspections twice a year
Public awareness and collective action are essential to halting the pest’s spread

Turkey supplies approximately 70% of the world’s hazelnut production. If this pest is not brought under control, it will directly affect the national economy and the livelihoods of approximately 400,000 families. Informed farming practices and timely intervention are vital for the future of our hazelnut orchards.

For a general pest management calendar, see our Spray schedule. For information on other pests, review our Hazelnut weevil guide.

📚 Hizal et al. (2015) - First Record of A. chinensis in Turkey 📚 Tuncer et al. (2019) - New Pest Species in Hazelnut Orchards 📚 Bozkurt (2018) - Invasive Insect Pest Management 📚 Trabzon Provincial Directorate of Agriculture and Forestry