Question
William, I am in NE Indiana. All of our white barked poplar are dying. The leaves turn dark brown and fall off. Yesterday I looked at the leaves and at the base of the leave where it attaches to the stem there is a round nodule. I opened several and there are small greenish almost yellow worms in them. The trees from pencil size to many years old have this and die. What is it and how can I stop it ? Spray ??

Doyle

Answer
Hi there . Sounds like
Poplar Petiolegall Aphid
Galls formed by this insect frequently attract attention because
of their conspicuous size and location on the leaf stems of poplars,
particularly Carolina poplar. Like many of the aphids, this species
has a very complicated cycle of development involving alternate
hosts in the family Cruciferae, mainly turnips, cabbage, and
Brussels sprouts. Briefly, the seasonal history begins with the
stem mother aphid which appears in late April. She settles on the
petiole of a poplar leaf and a gall begins to form around her. The
gall grows quickly and by July winged migrants are present within
it. These fly to various cruciferous plants. Here on the leaves
they give birth to other females which start colonies on the roots.
In late autumn winged forms are produced which migrate back
to poplar trees in the spring. In crevices of the bark on the trunk they give birth to males and females. After mating, the female lays
a single egg. This hatches into the stem mother which goes to the leaf petiole, thus completing the cycle.
Other than perhaps contributing to premature leaf-drop, it is uncommon for significant economic injury to be inflicted on poplar
trees by this aphid.
CONTROL
?Populations of this aphid fluctuate considerably from year to year. Control measures are not usually required.
Hope this helps,Bill