Question

trunk  

close view   I got an anwser from Matt about my oak tree but had a follow up question.  Background: I discovered an area of rot about 2.5~3ft wide and 4ft tall.  He mentioned not to use tools to scape out the rotten moist wood.... well I have already care fully remove the soft wood.  It is now open to light and air.  Is there anything I can apply that would kill directly on the open area?

If I shouldn't have removed the rot, did I do much harm.  The tree is about 8ft around and 60ft tall.  I attached 2 photos if that helps.  Thanks for any advise,

Answer
It is ok. No there is nothing that should be applies--wound dressing on trees will slow down the healing process.  The decay fungi are in the woody cells and over time will hollow out the tree trunk. So a fungicide would not help. BUT the fungi will not kill the tree. I would recommend fertilizing the tree with 10-10-10 fertilizer at the rate of 1 lb. per inch of trunk diameter scattered around the tree and watered in good. I would apply the fertilizer just before a rain event and you will not need to water. Apply now and again in the spring. This will increase the health of the tree and increase the growth rate of the cells that will grow on the edge of the wound.