The Kwanzan is a flowering cheery tree that does not produce any fruit. Instead of growing new trees from the pits of the fruit, Kwanzan cherry trees are grown from cuttings or grafted onto root stock of other varieties. The Kwanzan cherry tree is not tolerant of pollution and is so susceptible to serious diseases that it has a relatively short life expectancy of 15 to 25 years.
Several varieties of pests affect Kwanzan cherry trees. Aphids--soft, pear-shaped insects no bigger than the head of a pin, can be found on the underside of new leaves. They multiply rapidly and become adults in just seven days. Aphids live by sucking the juices out of the tree, causing leaves to wilt, lose color or become disfigured. Borers attack trees that are weak from being transplanted, drought, disease and stress. They lay eggs on the outside of the tree and the larvae bore their way into the woody parts, destroying the soft interior. Female scales secreted a waxy substance to cover and protect their eggs. When they hatch, the grubs suck the sap out of the tree. Heavy infestations can do severe damage. Spider Mites can be reddish brown or pale with black spots and are tiny and difficult to see on plants. They leave a fine web that looks like dust. They eat both the leaves and buds; the leaves can become spotted, turn yellow or turn brown.
Bacterial canker likes cool, wet weathers. Buds on the Kwanzan cherry tree may not open in spring and small greasy spots appear on the leaves when they open. The spots turn a dark brown and fall out, leaving holes in the leaves. The wetter the weather, the more likely the spots will grown and kill off the shoots. Another bacteria affecting Kwanzan cherry trees is crown gall, which lives in the soil for years. It enters the tree through wounds such as those from pruning. Once it is inside, it transfers part of its DNA to the DNA of the tree, causing galls, a wart-like growth. It can be as small as a fraction of an inch to several inches across.
Black knot infects the new shoots of Kwanzan cherry trees during rain storms or just after the tree blooms. The infection will not become evident for several months. Knots will appear on shoots, spurs or branches and other infections or insects may enter the knots. Knots can grow by at least an inch a year. Powdery mildew causes a white coating on the cherry tree's leaves that looks like simple dust. It appears as white spots that grow and come together to cover the whole leaf.