Question
Hi,
  I have a huge hackberry in front. Heard that for the second year has gotten some white-ish colored fungus all around the trunk right at the grass level. It has no definately form like some of the fungi mentioned for the hackberry. It is easy to pick off using a tool, but it does take some of the tree with it. I am afraid that at some point this tree will come down on its own and hopefully not in on our home.
 My question is, is this a fungus or rot? and is it treatable or should I arrange to have this wonderful tree taken down. Thanks!!

Answer
First lets get some terminology correct. A disease is caused by a fungi growing in the cells. There are root fungi and decay fungi. Both act differently and effect the tree differently. I think what you are asking is this a fungi that will kill the tree or a decay (rot) fungi??

Without looking at the tree it is next to impossible to tell. the best way would be by observing the foliage after it has completely leafed out. IF the foliage is green and full then the fungi is more than likely a decay fungi. Decay fungi attack the woody cells which are dead in the trunk. This fungi does not infect living cells and will not kill the tree. It can cause the tree to become hollow and over many years weaken the trunk. This will show up as large limbs breaking off and these limbs are hollow. At that point it should be inspected for a possible hazard tree--this depend son the tree condition and where it is located. This is many years down the road.

IF the foliage is sparse and light green or yellowish this may indicate a root fungi has begun to kill the root system. You will see dieback of the crown foliage and smaller limbs dying in the upper crown. This also will take some time to eventually kill the tree--maybe over several years. Fungi grow slow and the death is not all at once but limb by limb.

Both of these fungi can be offset by fertilizing the the tree with 10-10-10 fertilizer at the rate of 1 lb of fertilizer per inch of trunk diameter scattered around the tree and watered in good. Apply the fertilizer just before a rain storm and you will not need to water. This will increase the health of the root system and the overall health of the tree.

You did not say where you are but If you are unsure I would have a Forester take a look at the tree and see what they think. In the US the states have a Forestry agency that can come out and take a look --this is a free service. They have Forest Health staff Foresters also if you can get one of them to take a look. Check your local phone book for these agencies.