Wharf Borer Beetle

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PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

Illustrated identification guide — PestControlBasics.com

🔍 Identification

Adults: 10-15mm; orange-yellow with dark wing tips; resemble fireflies or soldier beetles; strong fliers. Larvae: up to 40mm; cream-colored; found in wet, submerged, or water-saturated wood. Exit holes: 8-10mm oval holes in wet timber. Found at docks, piers, boat houses, waterfront pilings, and any wood in contact with water or wet soil.

🧬 Biology & Behavior

Unlike most wood-boring beetles that require dry wood, wharf borer larvae specifically require wet or water-saturated wood with high moisture content. They're most destructive in intertidal and sub-tidal zones. Adults emerge May-August and are attracted to lights near water. A single log or piling can host hundreds of larvae simultaneously.

⚠️ Damage & Health Risk

Structural failure of docks, piers, pilings, and waterfront foundations; catastrophic collapse risk in heavily infested structures; significant economic losses to marine infrastructure.

🔧 DIY Treatment

Remove and replace severely infested wood. Pressure-treat replacement timber with appropriate marine-grade preservatives. For accessible wood above the water line: borate pressure treatment. Reduce moisture contact where structurally possible.

👷 When to Call a Pro

Marine engineering assessment for structural piers. Pressure treatment with creosote or copper-based preservatives for replacement timber.

❓ FAQ

How do I know if my dock has wharf borers?

Look for oval exit holes (8-10mm) in wet or submerged wood. Adults found at lights near water in summer. Push a screwdriver into suspect areas — heavily infested wood is spongy and yields easily. Marine surveyors regularly assess for wharf borer damage in waterfront property inspections.

Are wharf borers the same as shipworms?

No — shipworms (Teredo navalis) are bivalve mollusks that destroy submerged wood in saltwater. Wharf borers are beetles that attack wet wood at or above the water line. Both are waterfront wood destroyers but different organisms requiring different management.

Factor	Details
U.S. Range	All or most U.S. states
Regional Detail	Distribution varies — consult your local extension service for regional prevalence data.

Factor

Details

U.S. Range

All or most U.S. states

Regional Detail

Distribution varies — consult your local extension service for regional prevalence data.

📅 Treatment Timing Guide

Treating at the right time dramatically improves results. Pest control timed to the life cycle uses less product and achieves better long-term control.

Period	Action
Spring	Inspection and perimeter treatment before pest season starts.
Summer	Active monitoring and targeted treatments as needed.
Fall	Preventive treatment before overwintering pests seek entry.

Period

Action

Spring

Inspection and perimeter treatment before pest season starts.

Summer

Active monitoring and targeted treatments as needed.

Fall

Preventive treatment before overwintering pests seek entry.

💰 Professional Treatment Costs

Service Type	DIY Cost	Professional Cost
Initial inspection	Free (self-inspect)	$75–$150 (often credited to treatment)
One-time treatment	$30–$100 in materials	$150–$500
Annual service contract	N/A	$400–$900/year
Severe infestation	Often ineffective alone	$500–$2,500+

Service Type

DIY Cost

Professional Cost

Initial inspection

Free (self-inspect)

$75–$150 (often credited to treatment)

One-time treatment

$30–$100 in materials

$150–$500

Annual service contract

N/A

$400–$900/year

Severe infestation

Often ineffective alone

$500–$2,500+

Prices vary by region, property size, and infestation severity.

❓ Common Questions About 🪲 Wharf Borer

How do I confirm I actually have this pest (not something similar)?

The most reliable confirmation is a physical specimen — capture one and compare to reference images on this page. For cryptic pests (bed bugs, termites), look for secondary signs: frass, shed skins, mud tubes, or bites with a specific pattern. When uncertain, a professional inspection is faster than months of misidentification.

Can I treat this myself or do I need a professional?

DIY is effective for small, accessible infestations caught early. Professionals are worth the cost when: the infestation is inside wall voids or structural elements, multiple rooms are affected, you have health-risk pests (hantavirus, venomous species), or DIY has already failed twice.

How long until the infestation is completely gone?

Expect 3–8 weeks for most infestations with proper treatment. Insects with dormant life stages (pupae, eggs) extend the timeline because those stages are impervious to most insecticides. Follow-up treatments at 2 and 4 weeks catch each new cohort as they emerge.

What's the most common mistake people make treating this pest?

Treating only the visible pest population while ignoring the harborage site, entry point, or breeding location. Killing adults provides temporary relief but the population rebuilds from hidden egg cases, pupae, or new arrivals through unaddressed entry points.

🪲 Wharf Borer