A tree hosting a carpenter ant colony can often be saved, but their presence is an urgent warning sign. Carpenter ants only establish nests in wood that is already compromised, typically by moisture and decay. The true threat is the decay itself, which weakens the tree’s internal structure and creates the soft conditions the ants require. Saving the tree requires a two-pronged approach: eliminating the ant colony and addressing the underlying decay that allowed the infestation to begin.
Carpenter Ants: Pests or Symptoms of Decay?
Carpenter ants are not wood-eaters like termites, which digest wood cellulose. Instead, these ants are excavators; they use strong mandibles to chew and remove wood fiber, creating smooth galleries for nesting. Their diet consists primarily of proteins and sugars, often sourced from other insects, plant juices, or the sugary honeydew produced by aphids.
The ants prefer wood softened by moisture or fungal decay, making their presence a secondary problem. An infestation confirms a pre-existing structural defect within the tree. The ants take advantage of the compromised material, which is why a pile of coarse, wood-shaving debris, or “frass,” often accumulates near their entry points. Although the ants do not initiate decay, their continuous tunneling can extend the damage and compromise the tree’s integrity over time.
Evaluating the Tree’s Structural Health
Determining whether an infested tree can be saved hinges entirely on assessing the extent of internal decay. Arborists rely on advanced diagnostic tools to measure the amount of sound wood remaining, a process that goes beyond a simple visual inspection. The Resistograph, for example, is a micro-drill that measures the wood’s resistance as it penetrates, displaying variations in density to pinpoint decay.
A more comprehensive, non-invasive method is the Sonic Tomograph, which uses sound waves to create a colored, two-dimensional image of the tree’s cross-section. Sound travels slower through decayed or hollow areas, allowing the arborist to map the internal condition without causing significant damage. Studies suggest that a tree’s structural capacity can be compromised with as little as a 35% reduction in strength due to internal decay. If the decay is extensive, particularly compromising more than one-third of the trunk’s circumference in a critical area, the tree may be deemed a failure risk, and removal becomes the only safe option.
Actionable Steps for Treatment and Recovery
Saving a tree requires a dual focus: eliminating the carpenter ant colony and correcting the environmental conditions that caused the decay. Finding the parent colony, which contains the egg-laying queen, is paramount for permanent eradication. The colony is often located in the dampest wood, such as the base of the trunk or roots. Worker ants can be tracked by following their trails, particularly at night, or by listening for the faint rustling sound of their excavation inside the wood.
The most effective ant control involves targeted application directly into the nest galleries, often using insecticidal dusts or non-repellent baits. Baits are especially useful because foraging ants carry the slow-acting toxin back to the colony, eventually eliminating the queen and her offspring. Once the colony is managed, the long-term solution is cultural control, focusing on eliminating the excess moisture that attracts both decay fungi and the ants. This involves correcting poor drainage, removing wood debris and firewood piles near the tree, and trimming any limbs that touch structures. Modern arboricultural practices advise against sealing tree wounds or cavities, as this can trap moisture, accelerating internal decay and hindering the tree’s natural compartmentalization process.