Q: I have a 50+ year old pear tree that suddenly has shown signs of distress. After blooming and developing some fruit, the tips of some branches began to turn brown. It looks a little like freeze damage.
The problem has now spread to other branches in the lower part of the tree and appears to be taking over the entire tree. What’s going on?
A: You have a fine infestation of fire blight, a bacterial disease of apples and pears. Heretofore my recommendation was to spray each year with streptomycin at bloom…but streptomycin has become almost impossible to find on the market.
Copper-containing sprays (Kop-R-Spray, Kocide, etc) are bactericidal but they might cause russeting (freckles) on the fruit.
At this point in the disease cycle your best bet is to prune out all diseased branches, cutting at least 12 inches below the first visible symptom on each stem. Disinfect your pruner with a 1:10 mixture of bleach and water. Destroy the cuttings after removal.
Another avenue is to spray at leaf emergence each year with Messenger. This chemical causes a tree to think it’s being attacked, making it more resistant to disease and insects.