Ants won't kill your maple tree (Acer spp.) directly, but that doesn't mean an ant-infested maple tree isn't at some risk. The holes and tunnels left behind by carpenter ants can make tree limbs weaker and more likely to fall during windy weather. Holes made by ants may also make the tree more susceptible to diseases and pathogens that could kill it, even though the ants themselves will not. The biggest threat of ants in a maple tree, however, is that they will use the tree as a bridge to your home or other structures.
Why Ants Are Present
Ants have a voracious appetite for aphids, and aphids are commonly found in maple trees. Ants may be swarming your maple simply because it is providing food. Carpenter ants also live on or near trees for reproductive purposes. Ants don't eat the wood of the tree like termites do. Instead. they simply bore into the wood to create tunnels in which they nest and lay eggs. If carpenter ants are present on your maple tree, previous damage is likely the cause. Although carpenter ants can bore into the tree on their own, they are typically attracted to trees with knots, previous insect holes, cracks and rot. Trees with this type of damage are attractive targets to ants because they are easier to access.
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The Damage Ants Cause
It is estimated that around 75 percent of trees serve as home to carpenter ant colonies. In most instances, the ants and trees are able to coexist, and there is no reason to fear that the tree will die. However, carpenter ants do create holes in the tree. If other insects or lethal tree diseases find their way in through these holes, it is possible for the tree to get sick and die. This scenario is uncommon, but not impossible. The tunnels the ants leave in the trees can also weaken limbs. Weak limbs are much more likely to fall from the tree during high winds. It is also common for large ant colonies to set up satellite colonies near the tree. If the tree's limbs touch your home, you may find yourself living with ants in your home as well as on your maple tree.
What to Do
If the infested tree is not touching your home, you can opt to do nothing. The odds are high that the ants and tree will live in harmony and the tree will be fine. If the tree is touching your home, trim it back so that it no longer creates a bridge from the tree to your house. Remove any limbs that are clearly dead or damaged to prevent an accident. If you have concerns about the health of the tree, there are steps you can take to control the ants. If the tree contains aphids as well as ants, getting rid of the aphids will deter the ants. You can hose aphids off the tree with a jet of water from the garden hose. You can also spray the tree with an insecticidal soap for safe pest control with no residual effects. To treat the ants directly, apply a systemic tree and shrub pesticide. This type of pesticide is sprayed around the tree and taken up by its roots to provide insect protection for up to a year. A systemic pesticide is best for the tree, since it doesn't require that you drill holes into it.