It's hard to resist the appeal of a flowering cherry tree. Although modern varieties are easier to grow than their predecessors, there are still perils such as disease, pests and the effects of poor diet. The extra care that cherry trees require is worth it come harvest time—mid-summer for sweet cherries and late summer for sour cherries—when you can pick a ripe cherry off your very own tree and enjoy the fresh taste.
Both sweet and sour cherries suffer from brown rot and leaf spot, and sweet cherries also suffer from bacterial canker, according to The Backyard Orchardist. Brown rot is caused by a fungus where spores burrow their way under the skin of fruits that have been half-eaten by birds and insects. To treat, pick and throw away affected fruit and prune any branches with large numbers of affected cherries.
Leaf spot appears on leaves as brown or gray spots and is caused by a fungus that attacks the leaf tissue. The leaves eventually turn yellow and die. Check your trees for leaf spot regularly and remove and destroy any affected leaves.
Bacterial canker can kill a cherry tree if not caught soon enough. The bacteria enters the bark through wounds or pruning cuts, causing small, dark spots in leaves that turn to holes. The leaves whither and die and entire branches can be affected, causing buds not to open. To treat, prune any infected branches and destroy them, away from any other trees. In late summer and early fall, spray the tree with a copper-based fungicide.
Cherry trees can be damaged by pests, either birds or insects, according to Alan Buckingham in his book, Grow Fruit. Birds can strip an entire tree of buds in the early spring, then return in the summer to eat the fruit; holes can be eaten into leaves by the moth caterpillar; cherry fruitworms burrow into the fruit and lay their eggs and peachtree borers can take up residence inside the bark, killing the tree from within.
To protect your trees from birds, cover them with nets and fruit cages. To combat the moth caterpillar, apply a plant-oil-based spray in the winter to smother eggs. Inspect the tree in the spring and remove caterpillars by hand and apply a soil-dwelling pesticide. To prevent fruitworms, pick cherries often, destroy infested fruit and apply a pesticide. To kill peachtree borers, inspect the tree for holes where sap appears and probe the holes with a knife or wire to kill the borers. Treat the area around the trees to kill any borers in the soil.
Cherry trees need regular maintenance to ensure they are healthy. Nitrogen is the primary nutrient needed by cherry trees, according to Diane E. Bilderback and Dorothy Hinshaw Patent in their book Backyard Fruit & Berries, and without it, the leaves turn pale green or yellow with leaves near the bottom of the tree the most affected. Trees with nitrogen deficiencies will suffer from stunted growth. Treat with nitrogen-rich fertilizer.
A sign of boron deficiency is hard and shriveled cherries. Add one quarter to one-half of a pound of borax to the base of tree that is 20 feet or taller and less than one quarter of a pound to a tree that is smaller than 20 feet. If older leaves turn yellow between the veins, the tree may have a magnesium deficiency. This can be treated by applying Epsom salts around the soil at the base of the tree. A potassium deficiency will present as brown, scorched and curled leaves and can be treated with potassium sulfate fertilizer.