Each year we receive numerous calls
and see lots of samples of leaves and branches with strange growths, which are
known as galls. Galls are formed by the
plant because they are stung by an insect such as a mite, midge or wasp that
injects a growth developing enzyme that causes the plant to form these abnormal
growths. These galls usually do not cause any permanent damage to the plant,
but they can cause a homeowner to be alarmed when they see them.
An
example you might see on oak is a gall that forms in the twigs of oak. They are formed when a wasp lays eggs in the
bud of a tree and as the bud develops, the newly hatched wasp injects the
growth hormone, which causes the tree to form a gall around the wasps and they
feed on the juices from the gall.
The
other gall we will mention is one I like the name of. It is the roly poly gall. This is a gall that forms on the leaves of
oak and it looks like a huge green bubble of leaf tissue. It is hollow, but inside is an insect that
feeds of the nutrients that seep from the gall.
Control
of galls is generally not necessary and is difficult to achieve. By the time you see the gall, it is too late
to do anything about it. As I stated,
control is not usually necessary. It is
also very difficult for horse owners to tome sprays correctly to get adequate
control.
Another gall we often see in the
office is a gall on maple leaves. The maple
bladder gall is a red growth that forms on the leaves of silver maples and red
maples and sticks up from the leaf surface.
The red color attracts people’s attention to the galls, but they do not
cause any harm to the leaves. If
significant numbers on a leaf, you could get early leaf fall, which is not
serious.
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