Question
QUESTION: My friend has an large oak tree in her yard.  About 10 feet up there is a large split in the tree that was previously seeping sap but has now closed off.  However, at the base of the tree in line from where the crack or split was there is now a cave like hole wet with sap where there appears to be a nest of carpenter ants.  Also, on this same tree there is lots of lichen but also what appears to be random black patches about the size of 50 cent pieces possibly ranging to the size of a silver dollar.  These flat black patches are on the trunk of the tree in random places.  She had someone locally come out who told her that the tree needed to come down and that it would cost her $2000.00.  The tree seems strong.  It has survived several severe storms in the past two months with no limbs cracking off.  The crown of the tree still has it's leaves.  There is another oak about 12 to 15 feet from it in her front yard that doesn't have the black patches on it.  She is worried about the tree, does it sound like she needs to cut this tree down or is there a way to save it? Thanks so much

ANSWER: No If the foliage is green and full the tree is healthy. It sounds like the wood in the center of the tree is decaying and the tree may have some hollow places in the trunk. The living part of a tree is just under the bark and the bark protects the cells from decay fungi. When there is a wound to the bark decay fungi can get into the woody cells and start the eat away at the cells. carpenter ants some times make their nests in these decaying areas. The woody cells are dead cells and not associated with the healthy of the tree except for strength.
Trees can and do live many many years with their trunks completely hollow. Trees have the capability to seal off the decay fungi and slow the growth of the decay. IF the large limbs start to break off and the end near the trunk is decayed or hollow then the tree may have reached a point that it could be a hazard. And then it is only a hazard if it is locates near a structure that could be hit by a falling limb. Yours sounds a long way from that stage.

I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter and water it in  good, or wait just before a rain storm and fertilize and you will not have to water. This will increase the health of the tree and help slow the decay fungi. I would do this now and again after the leaves fall in the Fall.

 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. It is necessary to anticipate a carpenter ant colony and have a product ready at the start of construction. Once the nest is exposed, that portion of the colony will try to relocate to protect themselves.  


Should the tree be cut--Certainly some hollow trees may have so little healthy tissue surrounding the hollow area that they must be regarded as dangerous, but this is by no means the norm.  Trees do not become hollow overnight - it can take decades - and while the center of the tree (the heartwood) may be decaying, the tree continues to lay down healthy wood (sapwood) around the outside of its trunk.  This results in the formation of a cylinder, the strength of which depends upon the percentage of healthy to unhealthy tissue.

The first sign of the tree being a danger is large limbs breaking off and these are hollow. This means the decay has reach the limbs and is fairly extensive.  

I would not cut the tree but treat for the ants and fertilize.



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QUESTION: After surveying her tree more closely after posting the question (mistake), there are some missing leaves at the crown with some empty branches sticking out.  Put there are still healthy branches with leaves at the crown as well.  There are some slim branches (not major branches but ones that fork off of those) on the tree that have no leaves as well.  There are maybe 10 or 15 brown shriveled leaves on the tree total, but the tree is over 30 feet tall and 3 feet in diameter.  Again, even with some major storms uprooting several trees on the same street, she just lost two slim branches about 3 feet in length and some twigs.  With this info, is the answer still the same?  The tree is only about 15 from the house.  Thanks so much

Answer
Just 10-15 brown leaves is a very, very small percent of the leaves on the tree and it sounds like the tree is healthy. Losing small branches is normal. I would fertilize and if large live branches start breaking and these have decayed in the middle of the branch then you would want to re evaluate the health of the tree. But for now with what you have said it seems healthy and should live many more years.