ant nests are very common inside trees, especially older trees that
are hollow or have a significant amount of dead limbs and branches.
The nests are usually in rotted, decayed wood, although some nests
may extend into sound heartwood in the center of the tree. Carpenter
ant presence is an indication of rotting wood, and infested trees
whould be checked to determine whether the rot has weakened the
tree enough that it has become a hazard.
ants in trees are not directly harmful to the tree. Control is not
essential for the tree's health, as the ants are only taking advantage
of an existing situation of soft, weak wood in which to establish
their colony. Stress, mechanical injury, environmental conditions,
disease or other insects are responsible for killing limbs or sections
of the trees in which the ants are able to nest. Once injury has
occurred, wood decay can set in if moisture is present; it is the
wood decay that gives the carpenter ants the opportunity to colonize
the tree. Carpenter ants use knots, cracks, holes and old insect
tunnels to gain access to these areas.
of carpenter ants inside trees is difficult but can be done as a
way to reduce invasion of the ants into adjacent structures. It
is also possible for ant colonies located inside trees to form satellite
colonies inside a nearby home wall. Available controls are not likely
to permanently rid a tree of carpenter ants so retreatment every
year or so may be necessary. Dust insecticides (such as Sevin or
rotenone) labeled for use on trees in the landscape are suggested
for control. Apply the dust directly into the nest cavity.
Plugging or sealing tree cavities or treating tree wounds with wound
dressings is not advised. Such treatments are unnecessary and will
not eliminate nor prevent decay or carpenter ant activity. Also,
cutting down otherwise viable trees that happen to be infested with
carpenter ants is generally not necessary.
the Iowa Insect Notes, 2001