|Fire blight Erwinia amylovora creates scorched looking|
sections of leaves and branches of Bradford pear trees.
Fire blight - While originally Bradford pears were bred to be resistant to fireblight, that does not mean they can't get it. There are so many Bradford pears in the area, that there is a lot of disease pressure and a lot of host plants.
Fire blight is a bacterial disease that is spread by flies when the bradford pears are in bloom. The flies are the dominate pollinator of this plant - hence the malodorous fragrance from the flowers. The flower's scent is suppose to fool the flies who are looking for a place to lay their eggs and prefer rotten meat or dung. If the fly comes in contact with an infected host flower the disease will be spread to every susceptible flower it comes in contact with. Not a new problem around here, I have seen this problem on bradford pears for years.
The recommended treatment is to prune out the infected wood, 6-8 inches below the dead limbs. Make sure to clean pruners with an anti-bacterial wipe in between cuts. When the tree is in bloom it can be sprayed with streptomycin sulfate - a type of plant anti-biotic. However, I recommend just taking down the tree and replacing it with a tree that has no insect or disease problems. Bradford pears are short-lived with many known problems including splitting of the limbs. It is more expensive and time consuming to invest in saving this tree than replacing it with a better one. In addition, there are environmental and safety issues related to spraying antibiotics.
Additional information regarding fire blight can be found on http://pubs.ext.vt.edu/450/450-610/450-610.html .