ALLEGANY MOUND ANT ( Formica exsectoides )
Allegany mound ants, are capable of killing trees and can be found throughout the northeastern U.S. They are reddish brown and may be 3-6 mm long. These ants build mounds largely of coarse sand, dead twigs and leaves. It may take them several years to complete a mound, and it can be up to 3 feet tall and 6 feet in diameter when finished. Tunnels at depths of 6 feet, may radiate out from the mound for distances of 60 feet or more.
The primary function of the mound seems to be a place for incubation of eggs and/or pupae and the ants make every attempt to insure that the mounds stay as warm as possible. During the growing season, any vegetation that might shade the mound is killed by the ants. In the case of trees, the ants first tear away enough of the outer bark to expose the phloem and then flood the exposed area with formic acid. The formic acid causes coagulation of the contents of cells in and around the phloem and sap flow stops, preventing food from moving through the bark, and effectively girdling the tree.
In addition to killing trees, the mounds pose a physical hazard to mowing equipment. Eradication is necessary to prevent further tree death and possible injury to equipment. This must include the killing of the queen or she will quickly replace workers lost in an eradication effort. Burning with kerosene or gasoline, using napthalene or moth balls, flooding and mechanical disruption generally do not work. Some pesticides may be used to control these ants, but it is important that they be applied in such a way that the ants will carry some back into the mound to reach the queen and the other non-foraging ants.
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