Hazelnut Shot-Hole Borer (Xyleborus dispar): Symptoms, Traps and Spray Timing

What Is the Hazelnut Shot-Hole Borer?

The hazelnut shot-hole borer (Xyleborus dispar) is a bark beetle (Scolytidae) 2-3.5 mm long, dark brown to black, short and cylindrical. In the classification used by the Turkish Ministry of Agriculture and Forestry, this beetle’s official name is “Dalkıran”.

Unlike most other pests, the shot-hole borer eats neither the leaves nor the nuts. The female bores a round hole roughly 2 mm across into the bark of a branch or the trunk, enters the wood and excavates galleries there. What she feeds on inside those galleries is not the plant itself but an ambrosia fungus she cultivates on the gallery walls. The damage comes from the gallery severing the water and nutrient pathways.

Two Separate Pests That Share a Name

Along the Black Sea coast the name dalkıran is used for two different beetles, and their control timings are completely different. A wrong diagnosis means losing the whole season:

	Shot-hole borer (this page)	Longhorn beetle
Latin name	Xyleborus dispar	Oberea linearis
Size	2-3.5 mm, short and stout	11-15 mm, slender and long
Symptom	2 mm round holes in branch/trunk, sap seeping from them	The shoot tip dries out and stays hanging
What dies	The whole branch, eventually the entire bush	Only the shoot tip (10-30 cm)
Spray timing	Early July	Mid-May
Guide	This page	Hazelnut longhorn beetle

Damage Symptoms

• Round holes 2 mm across: clean, perfectly round entry points in the branch and trunk, as if made with a needle. This is the most reliable sign
• Seeping sap: sap oozes from the hole, leaving wet, dark stains. This is more obvious in humid weather
• Whitish frass: fine, pale wood dust collects at the hole entrance or on the soil under the branch
• Whole branch dying: because the gallery cuts the conducting tissue, every leaf fed by that branch wilts
• Bush death: under heavy attack the trunk becomes riddled with holes and the entire bush dies

Life Cycle and Adult Emergence

The shot-hole borer has one generation per year and overwinters as a mature beetle inside its gallery. Emergence comes in two waves, and it is the second wave that sets your control timing:

Stage	Month	What happens
First emergence	March – April	The first adults appear once air temperature reaches 18-20 °C. This wave is small in number
Main emergence	Late June – first week of August	80-85% of the population emerges in this ~6-week window
Establishment	June – August	The female bores her 2 mm hole into a new branch, builds a gallery and carries in the ambrosia fungus
Development	August – October	Larvae feed on the fungus inside the gallery
Overwintering	November – February	Mature beetles overwinter inside the gallery

Control Methods

1. Cultural Measures (The Most Durable Fix)

Because this beetle exploits weakness, the real control lies in keeping the orchard strong:

• Cut out and burn infested branches: cut holed and dying branches back into healthy tissue. Piling the cut branches at the edge of the orchard is not enough — the beetles inside will complete their emergence. They must be burned
• Do not leave dead bushes standing: a dead bush is the breeding reservoir for the next generation in your orchard
• Fix drainage, prevent drought stress: bushes standing in waterlogged soil or left dry through the summer are the first to be attacked
• Fertilize in balance: an underfed bush is colonized more easily. See our fertilization programme
• Prune for airflow: pruning guide

2. Biotechnical Control (Red Winged Sticky Traps)

For the shot-hole borer — unlike the longhorn beetle — traps genuinely work, both for monitoring and for mass trapping.

Infestation level	Traps per decare	Deployment period
High	6-8 traps	Late June – August
Moderate	3-4 traps	Late June – August

Traps should be hung so that they cover the July-August period, when 80-85% of the population emerges. The day adults start being caught is the day the chemical control window opens.

3. Chemical Control

Once the beetle is inside the gallery it cannot be reached by a spray. The target is the adults that have not yet bored into a branch:

• First application: early July — when adults start being caught in the traps
• Second application: 15-20 days after the first
• An additional application may be considered against the small spring wave (March-April), once temperatures reach 18-20 °C

Can It Be Sprayed Together With the Weevil and the Longhorn Beetle?

No — the three windows fall in different places:

Pest	Spray window
Longhorn beetle (Oberea linearis)	Mid-May
Hazelnut weevil (Curculio nucum)	Late May – early June
Shot-hole borer (Xyleborus dispar)	Early July

The longhorn beetle and the hazelnut weevil can be planned together in the May-June window, but the shot-hole borer arrives roughly a month after those two and needs a separate application. For the full season see our hazelnut spraying calendar.

Frequently Asked Questions

There are 2 mm holes in the branch — is this the shot-hole borer? Most probably yes. Clean, perfectly round holes as if made with a needle, with sap seeping from them, are the most typical sign. If there is fine whitish frass at the hole entrance, the diagnosis is settled. If instead the shoot tip dries out and stays hanging on the branch, the beetle you are after is the longhorn beetle.

When is the spray applied? The first spray goes on in early July, the second 15-20 days later. Do not set the timing by guesswork — hang red winged sticky traps from late June and let the catches tell you. Ask your provincial directorate of agriculture for the dates specific to your region.

Why did it appear in my healthy orchard? The shot-hole borer usually targets stressed bushes, but under heavy population pressure it will settle in healthy ones too. If there are neglected or abandoned orchards nearby, that is your source of infestation. In that case cultural measures alone will not be enough and must be backed by traps and spraying.

Are traps enough on their own? Under light infestation, 3-4 traps per decare together with cutting and burning the infested branches may be sufficient. Under heavy infestation, traps only suppress the population and must be backed by spraying.

Should I remove a dead bush? Yes. As long as a dead bush stays in the orchard, the beetles inside complete their development and spread to neighbouring bushes the following year. Pull it out and burn it — a single dead bush left standing can undo the entire control effort.

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This guide is based on data from the Hazelnut Research Institute of the Turkish Ministry of Agriculture and Forestry and on the control announcement issued by the Giresun Provincial Directorate of Agriculture and Forestry. Always make spraying decisions in consultation with an agricultural engineer.