OSU Extension Catalog

Pest identification

• Adults are small orange flies 2 mm (1/16") long.
• Yellow-brown to orange-colored eggs, each with a red spot, can be seen with a 16× hand lens on new needles and buds.
• Legless larvae are 2 mm (1/16") long with white, yellow, orange, or olive-green bodies, and no distinct head.
• Contarinia pseudotsugae, C. constricta, and C. cuniculator are all very similar in appearance and behavior.

Biology and life cycle

• Adults typically emerge in April to May and lay eggs on buds and new growth. Larvae emerge after a few days and burrow into needles, forming galls, where they spend the summer.
• In fall, larvae emerge from galls, drop to the ground, and enter the soil.
• In spring, larvae pupate in soil before adult emergence.
• Individual adults live only a few days; however, emergence occurs over several weeks.

Only affects Douglas-fir

Growing years

• Monitor for adult Douglas-fir needle midge emergence to effectively time spray applications. (See Overview of Trapping and Monitoring Options.)
• Use the USPEST.ORG online phenology and degree-day model for Douglas-fir needle midge to predict adult emergence.
• Place 5 traps per field or 10 per acre; check frequently to time sprays, if needed.
• Record locations of needle damage found in late summer to scout and place traps accordingly the following spring.
• Note: Traps will collect insects other than needle midges, including non-pest species of midges.

At harvest

• Douglas-fir needle midge is in larval stage feeding inside the needles.
• Feeding damage includes yellowish swellings (galls), yellowing needles, and premature needle drop.

Threshold

• Some trading partners, such as Mexico, have zero tolerance for selected species of Douglas-fir needle midges.

Growing years

• Remove and destroy heavily infested trees in the early fall, before larvae exit needles.
• Time insecticide application based on collection of adults in emergence traps, field scouting, or the USPEST.ORG online phenology and degree-day model for Douglas-fir needle midge.
• Make first insecticide application based on collections in traps, scouting, weather, and bud development.
• Note: Insecticides are effective only against adults. (Visit the PNW Insect Management Handbook.)

At harvest

• Exclude trees with signs of Douglas-fir needle midge damage when shipping internationally.
• C. constricta is the only species on the Mexican quarantine list; however, try not to ship any damaged trees, since misidentification is likely and Douglas-fir needle midges have caused the most load rejections by Mexico. (See Pest Quarantine Information.)
• Note: Shaking is not 100% effective, and infested needles may remain on trees.

Life cycle

Management