Q: Can you tell me what is wrong with my two Bradford pear trees? They have black leaves and dead ends on many of the branches.
A: Your pears have fire blight. This disease is caused by bacteria rather than fungi, so fungicides do not control it. A bactericide containing streptomycin sulphate (Agri-Mycin, etc) (click for sources) can be sprayed on trees at five day intervals when the blooms are open. This product is expensive and must be used during bloom time.
Another product, Serenade, is a bacteria that helps control fire blight. It too must be used at bloom time.
Since it requires specific environmental conditions to develop, the disease is wide-spread in some years but scarce in others. ‘Bradford’ flowering pear is actually moderately resistant to fire blight while ‘Aristocrat’ and ‘Capital’ are highly susceptible.
In your case, the damage has already been done and the right time to spray is past. Your best bet now is to use a pole pruner to remove the affected black twigs. This will be a two-person job because the blades of the pruner must be disinfected between each pruning cut. Mix a 1:9 solution of alcohol:water and pour it into an inexpensive spray bottle. As you work, remove each branch from the tree and lower the pruner so your partner can disinfect the blades.