I have a 12 year old Bradford pear (about 25 feet tall) that has fire blight for the last three years. I had a local tree service that is considered in high regard treat the tree for two years, but this year (the third year) the blight is back again and even worst then before. Do you have any recommendations other than, one, cut out infected branches about 8 to 12 inches past their infection area and two, clean the cutting tools with a 10% bleach solution between each cut. Also, since the tree has lost about 25% of its branches, is it time to not even try any longer and just replace the tree?