As summer is coming on, so is the threat of fire blight, a nasty killing problem for fruit trees and other plants. It comes on the wind and can't be prevented, but it can be cured. I had fire blight (looks like parts of the plant are charred) several years back on my dwarf pear trees and successfully used this treatment. The blight itself is an alkaline composition, so I simly made up a solution of 1 part white vinegar to 3 parts plain water and sprayed it over every part of the tree except flower buds and fruit. Any infected stems will have to be cut off just into good growth using secatur blades first dipped in straight vinegar so you don't pass the infection on to other parts of the tree. I repeated the spray 2 weeks later and the blight cleared up and never returned.
I've also used this to treat rust on fruiting bushes, but reduce the vinegar to 1 part against 4 parts water. The plant leaves might fall off, but they will grow back next year. Also spray the ground around the plant base. I can live with a few dead worms rather than a dead plant.