The poplar twig gall fly generates a circular gall on the new twigs.
This gall remains in place and grows and enlarges as the plant matures, giving it a gnarled, knobby look.
Plants appear to be unaffected by galls.
Cytospora canker may form around a gallon on rare occasions.
Hosts plants:
Aspen (Populus tremuloides and P. grandidentatum) seem to be host plants.
Damage insect caused by Poplar Twiggall Fly:
On fresh twigs, the poplar twig gall fly develops a spherical gall. Galls appear as smooth swellings on twigs and branches in the present season. Even though these ancient traumas leave a permanent scar on the tree, they do not appear to threaten its health. Although the growth of buds next to the galls is hindered, areas galled by the poplar twig gall fly usually continue to grow. On the other hand, galled tissues continue to develop and expand, attracting attention and causing particular concern.
Description of Sap Suckers:
Sapsuckers are a species of woodpecker found in North America. Sapsucker wells are immediately identifiable. With its chisel-like beak, the bird drills a dozen or more tiny holes in a horizontal line, each less than half an inch apart. Then it returns to suck up the sap that has trickled out again. The bird produces the second row of holes slightly above the first when the flow begins to wane, generally after a few days. A sapsucker at work is identified by a rectangular pattern of nicely spaced holes in tree bark. The yellow-bellied sapsucker is the most common. It lives in Canada’s and Alaska’s frigid evergreen woods. It migrates east of the Rockies and spends the winter in the Southeast United States.
Life history and habitat:
The poplar twig gall fly overwinters as a full-grown yellow-green maggot within the gall. Pupation happens in the gall in late winter or early spring. Adult flies emerge from the pupae and become active during new growth. Adult flies are 1/6 inch long, stout-bodied, lustrous black insects. Females migrate to the budding twigs after mating and place eggs into the stems. These eggs develop into larvae, which create the characteristic swelling in response to their eating. Each year, there is one primary generation. Observations suggest that a few flies may have a second generation during hot seasons that allow more extended development.
