Contarinia oregonensis (Cecidomyiidae)

Douglas-fir cone midge


Adults:

Adult Contarinia oregonensis. This is not the injurious stage. Adult flies are small, only 3-4 mm long. Adults have just 1 pair of wings. Abdomen is orange, and female flies have a long retractile ovipositor.



Larvae:

Late instar Contarinia oregonensis larva. Mature larva is small and orange coloured. The feeding larvae live in small chambers within the seed.  The unusual chamber formation as a plant response to feeding by larvae results in galls being formed.



Damage:

Feeding by Douglas-fir cone midge larvae has resulted in galled seeds. Adult female lays eggs near base of cone scale in newly opened flowers. When the egg hatches, the larva tunnels into the young cone scale and forms a gall. The gall fuses the developing ovule to the scale. Severe infestations will destroy all seeds in the cone. The larva remains in the cone until it completes its development, it drops to the ground during wet weather in autumn. Cocoons are spun in the litter and overwintering occurs in prepupal and pupal stages.



Principal Hosts:

Douglas-fir.

Economic Importance:

This insect probably occurs throughout the range of Douglas-fir, but it is generally more serious in wetter coastal areas than in the drier interior.

References and Links:

EAG: 548; FC: 417.

Additional Images:

Chambers in a seed infested by Douglas-fir cone midge. Tiny eggs at base of bracts. Normal and galled seeds. Sagittal sections through a healthy cone and one where feeding by Douglas-fir cone midge larvae has resulted in galled seeds.