PestHigh Severity

Douglas Fir Gall Midge

Contarinia pseudotsuga

A small midge considered the most significant pest of Douglas fir seed orchards, capable of destroying up to 70% of seed crops. Orange maggots cause galls around seeds, killing them or fusing them to cone scales so they cannot be shed or extracted.

Peak Season: Overwintering: As larvae in soil under infested treesPupation: Early spring as buds expandAdult emergence: Early April, continuing 4-5 weeksEgg laying: During bud expansion and needle elongationLarval development: Throughout summer in gallsLarval emergence: Late summer, dropping to soil
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Douglas fir gall midge showing characteristic needle galls and orange larvae

Identification & Symptoms

What to Look For

Galls forming in the vicinity of seeds within cones
Orange maggots (2mm long) visible in galls
Seeds killed or fused to cone scales
Seeds unable to be shed or extracted from cones
Needle galls causing bending and discoloration
Irregular emergence holes appearing as slits or ruptures
Dark brown areas developing on affected needles

Potential Damage

Destruction of up to 70% of seed crop in orchards
Complete seed loss in heavily infested cones
Prevention of natural regeneration
Economic losses in seed production operations
Reduced cone and seed viability
Secondary fungal infections through emergence holes

Lifecycle

Overwintering larvae pupate in soil in early spring as buds expand. Adults emerge over 4-5 weeks starting in early April. Females use long ovipositors to place orange eggs in expanding buds and elongating needles. Hatching larvae create galls around themselves, developing through summer before emerging and dropping to soil in late summer.

Professional Treatment Approach

1

Imicide applications targeting adult emergence in early spring

2

Systemic Imisol treatments for comprehensive protection

3

Time treatments with bud expansion and adult emergence

4

Soil treatments to target overwintering larvae

5

Monitor for adult activity beginning in April

Recommended Mauget Products

Imicide

Professional-grade treatment specifically effective against douglas fir gall midge.

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Imisol

Professional-grade treatment specifically effective against douglas fir gall midge.

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