Q. How did I rid or prevent my pear tree of Black Leave Disease?
Your pear tree probably has fire blight
Fire blight is one of the most destructive diseases of apple and pear trees. Outbreaks are sporadic in most parts of the Northeast, but can cause extensive tree damage when they do occur. Therefore, the necessary intensity of control programs will vary considerably for different plantings and in different years. The state Cooperative Extension Service is the higher athority on this matter. See their link here: https://ecommons.cornell.edu/bitstream/handle/1813/43095/fire-blight-FS-NYSIPM.pdf
You can also consult with our state extension agent "Jerry", who is available usually Mon-Fri before 12 noon. 914 285-4620
Hope this helps.