PestMedium Severity

Douglas Fir Cone Moth Larvae

Barbara colfaxiana

The larval stage of the Douglas fir cone moth, representing the most damaging phase of this pest. Larvae are initially yellow-white with black heads, later becoming pink to yellow with brown heads. They create tortuous resinous tunnels through cone bracts and feed directly on scales and seeds.

Peak Season: Egg hatching: Early summer following egg depositionActive feeding: 2-month period during cone developmentPeak damage: Mid to late summer during seed formationPupation: July-August within cone structuresOverwintering: As pupae in protective cocoonsExtended cycle: Some larvae may have biennial development
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Douglas fir cone moth larvae showing tunneling damage and resinous cocoons in cone scales

Identification & Symptoms

What to Look For

Visible larval tunnels with resin coatings through cone bracts
Resinous exudations and castings extruded from tunnel openings
Direct feeding damage on cone scales and seeds
Larvae visible within cone structures during dissection
Progressive cone deterioration from internal feeding
Papery resin-coated cocoons near cone axis

Potential Damage

Direct seed destruction through larval feeding
Prevention of seed development and maturation
Cone structural damage from extensive tunneling
Interference with natural cone opening mechanisms
Complete loss of seed viability in heavily infested cones
Resin plugging preventing seed release

Lifecycle

Larvae hatch from eggs deposited on cone bracts and immediately begin boring resinous tunnels. They feed first on cone scales, then progress to seed consumption over approximately 2 months. Mature larvae pupate near the cone axis in resin-coated cocoons. Some larvae may extend development over two years.

Professional Treatment Approach

1

Target treatments during early larval stages for maximum effectiveness

2

Imicide applications when larvae are actively tunneling

3

Remove and destroy infested cones to reduce larval populations

4

Systemic Imisol treatments for comprehensive protection

5

Monitor cone development during vulnerable periods

Recommended Mauget Products

Imicide

Professional-grade treatment specifically effective against douglas fir cone moth larvae.

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Imisol

Professional-grade treatment specifically effective against douglas fir cone moth larvae.

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