Pear trees attacked by disease

Credit: E. Yada

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Q: All of my pear trees have some sort of disease. I live in North Saanich on Vancouver Island. We have had quite a damp, late spring. The new shoots look dead from the tip to about half way down. The bark is split and peeling and is quite dark. The leaves have either disappeared or have turned brownish black and are crispy.

The rest of my fruit trees -plum, apples, cherries are in great shape. I band all the trees in the fall and spray them with horticultural oil and lime sulphur when dormant. I did some summer pruning on the pear trees. What is going on? Am I going to lose these trees? Will this spread to my other fruit trees? What should I be doing?

The problem is caused by a cool, wet weather disease organism (Pseudomonas syringae pv. syringae) ‘Blossom Blight’ common here on the coast. This bacteria can blacken buds, cause leaf shot-hole and stem or trunk cankers. Spreads very easily by water. Plants grown under stress are also more susceptible.

Avoid possible freezing damage to the pear tree. Minimize pruning wounds which can serve as entry points for the disease. Sterilize tools when pruning (1 part Lysol: 9 parts water). Make sharp cuts. Prune in either January or February, or drier weather (mid-summer). Make cuts into clean green wood at
least 15 to 20 cm away from diseased tissue. Maintain proper growing conditions, e.g. adequate pH, water, nutrient, air circulation. Avoid excessive succulent growth and remove dead leaves and branches. Minimize weed growth which may harbor the disease organism. Copper spray can be used,
as directed on label, in October and at leaf drop, plus spring time at reduced rate.