Common problems with cherry trees include brown rot, black knot, leaf spots, cankers and nutrient deficiencies; these trees are also prone to a number of fungal infections. Common pests include the black cherry aphid.
Brown rot is caused by the monilinia fructicola fungus. The fungus leads to browning and collapsed flowers, cankers on the twigs, browning fruit and shriveling fruit. To combat this fungus, spray the tree with fungicide when it starts to flower and touch up the spray when most of the tree is in bloom.
Black knot describes a condition that results in black or dark brown knots on the branches and twigs, which grow each year. It causes weak and brittle branches and may cause growth to die. To manage the problem, prune the affected area off of the branch. If the black knot affects the trunk, cut the knot out of the trunk. Spray the tree with fungicide before and after flowering to prevent the problem from returning.
A fungus called coccomyces is the culprit behind leaf spots. The spots are usually circular and are purple, brown or red. They usually cause the affected leaves to turn yellow and fall off the tree. To fix the problem, spray the tree with a fungicide when the new leaves emerge.
Large cankers that cause stunted growth or dead branches are often the result of a fungus called leucostoma cincta. Other symptoms of the disease include gum in the inner bark and blackened crusts around cankers. To fix the problem, prune off branches affected with cankers.
Not all cherry tree problems result from diseases. Nutrient deficiencies can cause yellowing leaves, pale leaves, dropped leaves and dead branches. The trees are susceptible to iron and magnesium deficiencies. To fix the problem, test the soil to make sure that the pH levels do not exceed 7.3. If the soil pH levels are not too high, spray the foliage with an iron or magnesium spray or add a soil amendment.
The black cherry aphid is a common pest. It is a small black aphid that can attack leaves and shoots, causing stunted growth and damaged leaves. To get rid of aphids, spray the tree with insecticide.