Pears come in both ornamental and fruit-bearing varieties, both of which produce beautiful spring blooms. This makes them popular in landscaping and backyard orchards. Difficulties arise because many cultivars are highly susceptible to a few diseases. Proper maintenance can help prevent disease in pear trees. However, if it occurs, recognizing the symptoms and knowing how to react could mean the difference between a minor problem and the loss of the pear tree.
Bacterial diseases can cause serious damage. The most damaging bacterial disease is fire blight, to which most fruit-bearing varieties and many ornamental varieties are highly susceptible. Insects can play a key role in spreading fire blight and can be considered part of the disease life cycle. Fungal diseases such as leaf spot can damage a tree and render its fruit useless. Crown rot is another fungal disease.
Leaf spot can be recognized by the small, purple to black spots that appear on leaves, petioles, shoots and fruit. As the disease worsens, the leaves will drop prematurely and the fruit will crack and fall. Crown rot is harder to detect. Affected pear trees will grow poorly, have smaller leaves that turn red and gold prematurely, brightly colored but small fruit and an inadequate root system. Fire blight leaves blossoms, twigs and shoots looking as though they have been scorched. They soon turn black and die.
Leaf spot fungus grows well in moist warm weather. High winds and splashing rain are responsible for spreading the disease to uninfected tissue, and serious damage can be caused by midsummer. Crown rot can occur at anytime, but its frequency seems to rise in situations where overwatering is present. Fire blight does the most damage during the blooming phase. Once present, though, the disease can overwinter in wounds on the tree and strike up its assault the following spring with increased intensity.
Fungicides are effective in treating leaf spot. Applications should be made according to manufacturer’s directions. A copper fungicide is used to treat crown rot. An alternative is to dig out the crown and allow it dry out over the summer. It should be covered with sand or pea gravel, weed fabric and topsoil before winter. Fire blight requires immediate pruning of infected tissue. Pruning tools should be disinfected between cuts with a 10 percent solution of bleach. Cuts should be made 8 to 12 inches below the visible sign of infection. You can treat the tree three times in the spring, at 5-day intervals, with streptomycin.
Leaf spot can cause pear trees to defoliate by midsummer. Fruits are usually scarred, scorched and unusable. Crown rot will damage the overall health of the tree which in turn produces small fruit or causes autumn leaf color to occur ahead of schedule. Fire blight causes branches to die and, left untreated, can kill the pear tree in a few years.