ants on aspens - Knowledgebase Question

Golden, Co
Avatar for sheriakes
Question by sheriakes
July 12, 2010
I have many aspen trees some over 10 years old about 10-18 ft tall. Most are infested with big black ants. They have killed a few of them already. How do I kill the ants and not the trees or other plant life?

Answer from NGA
July 12, 2010
Carpenter ant nests are very common inside trees, especially older trees that are hollow or have 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 ants in trees are not directly harmful to the tree. Control is not essential for the tree's health, because 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 and 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.

Control of carpenter ants inside trees is difficult but can be done as a way to reduce invasion of the ants into adjacent structures. Available controls are not likely to permanently rid a tree of carpenter ants so retreatment every year or so may be necessary. Dust insecticides containing pyrethroids or carbaryl labeled for use on trees in the landscape are the best approach. Apply the dust directly into the nest cavity.

Best wishes with your aspen trees.

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