Almost 3,000 different varieties of pears can be grown in backyard gardens or commercial orchards. These include the Anjou pear, mostly used for baking or in salads; the Bartlett pear, usually used in canning and sometimes for baking; the Comice pear, which works well in salads; and the Asian pear, which appears more like a golden apple and is often referred to as an apple pear. While pear trees are fairly easy to grow, they are susceptible to problems just like other fruit trees.
Pear trees are especially susceptible to fire blight, a disease caused by a bacteria transmitted by bees and other insects that travel from flower to flower. Infestations cause the new branches to die off and bend downward. The bacteria forms cankers, where the bacteria live through the winter. Because the bacteria destroys the flower blossoms, the tree does not reproduce. When the blossoms and branches wilt, they turn black, but when the leaves die, they stay on the tree and make it look as if the tree has been burnt. The disease can be controlled by chemical sprays that kill the bacteria, or by hand pruning the dead branches carefully so the bacteria is not spread by pruning shears or contaminated branches.
Codling moths are particularly damaging because there are several generations each year. The first generation of adult moths lays eggs on the leaves of the pear tree; the larvae first feed on the leaves of the tree and then move on to the developing fruit. These larvae then emerge and crawl down the tree to pupate in cracks between the bark. When the adults emerge, they will lay eggs right on the fruit; the young caterpillars will then feed directly on the fruit. The moths and caterpillars can be killed with insecticides applied before or after the flowers have blossomed.
Pear scab, or black spot, is a fungus that causes brown lesions on the leaves, twigs and fruit of the pear tree. The infection may cause the fruit to become misshapen and creates cankers on the branches, where spores are produced. The spores spread the disease, especially during wetter periods of the year. When infected leaves fall off the tree, the fungus stays in a dormant state on the leaves through the winter. Younger fruit is more heavily damaged than more mature fruit. It is important to monitor the trees during wet periods. The longer the leaves are wet, the more likely the tree is to become infected. A fungicide can be applied when buds first appear.
An insect known as the pear psylla feeds on the sap of the pear tree leaves and produces sticky honeydew that will eventually cover most of the tree and cause stress and stunted growth. The adult psylla lays eggs on leaves and branches. Unfortunately, these insects are not easily killed with insecticides; however, an oily spray added to an insecticide may work if it is sprayed on the tree during the dormant phase.
The pear slug comes from the pear sawfly. The slug is actually the larvae of the fly, and it will feed on the leaves of the pear tree, leaving the top part of the leaves thin and lacy looking. Most insecticides will kill the pear slug and the sawflies. Wood ash sprinkled on the leaves will also help to repel the insects.