Cecidomyiid. Undescribed.
Big Bud

Hosts: Populus trichocarpa [tristis]

These galls (photo 27) are most easily spotted during the fall and winter when the leaves are off the trees. The gall is an enlarged terminal or side bud and will stay attached to the plant for some time, even after the gall has died and turned brown and brittle. In fact, a dead big bud from the previous year can frequently be found on the same twig with a current year's big bud.

Attacked buds begin to swell in early May and are often covered with a yellow sticky resin. The bud is enlarged because the bud scales and stipules are thicker than normal. Nestled between the thick scales, you should be able to find several very small orange larvae that are often bathed in yellow plant resin. These are the midge larvae. They use the spaces between scales as their larval chambers.

In August, the fully formed galled buds are green and about 2.5 cm long and 1.5 cm wide. All bud parts are enlarged. The outer scales are green, and the inner ones are yellow to cream-colored. By mid-October, the 5 to 15 larvae in each bud are white (because of stored fat) and have a prominent sternal spatula. Most larvae occur near the center of the big bud and are often awash in the sweet-smelling resin. The bud tissue near a larva is sometimes brown. The larvae probably feed by scraping the cells on the surface of the bud parts. Feeding may cause the browning.

?Rhabdophaga sp.

Enlarged buds, larvae deep red, on western balsam [Populus trichocarpa], midge

Dasineura sp.
Big-bud-gall midge
[Page 66]

Hosts: black cottonwood [Populus tristis]

The galls are composed of greatly enlarged bud scales covered by orange, sticky liquid.

Dasineura sp.

Enlarged winter bud

Host: Populus trichocarpa [tristis]

Infested buds are conspicuous in summer. The red larvae are immersed in a sticky exudate between the bud scales. Larvae form cocoons in fall, diapause as larvae, and pupate in spring. Infested buds burst, but the leaves do not develop.

Range: WA and OR