Question
QUESTION: I am wondering if it would be carpenter ants drilling holes in my oak tree.  I discovered a mound about the size of your hand of little "tubes" about 1/4 inch long at the base of my tree, and then noticed large ants crawling up the tree into a natrural-looking hole. There was another hole above it that looked like a man-made hole about the size of my pinkie finger in diameter.  How can I protect my tree and get rid of them?  They were coming from either the nearby fence or the neighbor's yard.

ANSWER: Carpenter 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 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.

Control 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


Control of carpenter ants in trees is warranted if there are indications that ants are entering homes from colonies in trees. If there is evidence of this, the best control is to bait the colony.
Baits, such as Terro. Baits tend to be slower-acting than other forms of carpenter ant control, but they are easy to apply and give good results, especially when the nest can't be located. The ants themselves will carry the bait back to the nest, which usually provides colony elimination.

There are a few baits available to nonprofessionals for carpenter ant control. Most retail products are liquid or granular formulations containing hydramethylnon, sulfluramid, abamectin, or boric acid. An inexpensive liquid bait of 1% boric acid in a 10% sugar water solution can be mixed at home, but it is very slow acting and must be constantly replenished. Baits vary a great deal in their effectiveness. Carpenter ants have complex food preferences, and some of the sugar-based baits will not be attractive to the ants long enough to be successful.  

If the nest is exposed  you can use a liquid or aerosol ready-to-use insecticide, such as bifenthrin, cyfluthrin, deltamethrin, or permethrin. Spray the insecticide directly into as much of the nest as possible. The more of the colony that is exposed, the better your chance of destroying it.  



---------- FOLLOW-UP ----------

QUESTION: Actually, I am not even sure they are carpenter ants.  I'm wondering what would be making a pile of little brown stick-like things about 1/4 inch long, that look like something you would have if you took a tiny core sample out of the tree.  The pile is about half the size of my hand and it at the base of the tree under a spot on the trunk that seems to be pushing those tiny "core samples" out.  If I didn't know better, I would almost say the tree is bleeding, but not sap or anything viscous.

Answer
The carpenter ant comment sent me on the wrong track. This sounds like an insect called a borer. Certain specific external signs indicate internal red oak borer damage in host trees: extruded frass , discolored bark patches , wet spots , wood slivers , and exit holes . These surface indicators have been associated with different stages of larval development during the insects' 2-year life cycle, and therefore can be associated with defects in lumber and other wood products.

The fine larval frass  is found during the first fall and winter after eggs hatch. Wet spots  and medium-sized larval frass can be found during the first spring and early summer. Discolored bark patches  and large quantities of larval frass occur in the second fall and winter . Wood slivers are extruded in the spring and early summer just before the adult emerges . The adult exits through an oval hole which it chews in the bark .

The trunk of the tree where the damage is showing should be sprayed with an insecticide. Onxy or Merit are two insecticides that will work well. There are others under other names that also will work. Look on the label for directions for borer control on trees. Check with your local garden type store for these products.

Borers usually attack trees that are under stress. This fall I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb of fertilizer per inch of trunk diameter scatterered around the tree and watered in good. Apply just before a rain storm and you will not need to water it in. This will increase the overall health of the tree. and help the tree ward off attacks.