Ornamental trees that reach between 30 and 40 feet tall, Cleveland pears display showy white blossoms in the spring. These pear trees have a high level of resistance to most diseases, but resistance does not mean immunity.
Fire blight affects the blossoms, fruitlets and shoots of Cleveland pear trees. Entomosporium leaf spot, another common fruit tree disease, appears as circular spots on the leaves, and powdery mildew and phytophthora root rot also affect foliage. Crown gall harms the roots and stems of Cleveland pear trees.
A bacterium more prevalent in warmer climates causes fire blight. A different bacterium, which enters the trees through a wound, leads to crown gall.
The fungus entomosporium causes leaf spot during cool, wet weather in the spring and fall. Powdery mildew, another fungal growth, appears as a dusty white coating over the leaf surfaces and other parts of the tree. Phytophthora root rot can develop on Cleveland pear trees if the soil around the base of the plant stays wet for prolonged periods of time.
Fire blight causes disfigurement and death of the infected limbs on the Cleveland pear tree. The flowers, leaves, twigs and new shoots of infected trees will quickly wilt and turn from brown to black. If the tree is covered with infection, it will appear scorched.
Entomosporium leaf spot on Cleveland pear trees appears as tiny, circular, bright red spots on the upper and the lower surface of young leaves. Mature leaves will have an ash brown to gray center in the spot, with a thin brown margin. If the tree is heavily diseased, the spots join together to form large, irregular blotches.
Crown gall symptoms include rough galls forming at the crown, which is the point on the tree where the roots join the main stem at the soil line. The galls range in size from 1/4 inch to more than 1 foot in diameter.
Powdery mildew begins as an unobtrusive, typically circular, powdery white spot on the leaves that expand and combine to form a continuous matt of mildew. Leaves infected by phytophthora root rot will appear drought-stressed and can die quickly in warm weather.
Fire blight can kill Cleveland pear trees along with other fruit trees and ornamentals living nearby. Damage from a light infection of entomosporium leaf spot is primarily cosmetic, but severe infections may result in heavy leaf drop early in the season. Severe defoliation in any tree slows growth and increases its sensitivity to cultural and environmental stresses.
Crown gall will limit your Cleveland pear tree's growth and productivity. Powdery mildew seldom kills infected trees, but it can disfigure and spreads easily to other nearby plantings. Cleveland pear trees infected with phytophthora root rot can survive several years before the disease kills it.
Bactericides and fungicides can treat specific diseases on your Cleveland pear trees. You also can prevent the contraction and spread of disease. Remove and discard the infected limbs and twigs and rake away fallen leaves. This will help reduce the amount of overwintering fungal spores. Prune your trees in the late winter before the buds break. If you prune in the summer, you are encouraging new growth, which is susceptible to bacterium and fungal attacks.