Kwanzan cherry trees are relatively short-lived trees, since they are not particularly hardy and are susceptible to a number of diseases and infections. While your Kwanzan cherry tree will probably not live for decades and decades, you can help prolong its life and keep it looking beautiful for a decade or two by being aware of the signs and symptoms of Kwanzan cherry tree disease and knowing how to deal with them.
Kwanzan cherry tree disease can attack any part of the cherry tree. In many cases, a disease weakens the tree at first, leaving it susceptible to other infections. As the disease spreads throughout the tree, more and more symptoms will manifest themselves until the tree eventually dies because of an inability to absorb or transport nutrients.
Leaf-spot diseases come in several types. Anthracnose causes purple, yellow or brown spots to form on leaves. Left unchecked, these spots may grow and cause the leaves to stop functioning or even fall off the tree. Shot-hole disease causes small, black holes on the leaves that expand and cause the tissue in the middle of the spot to rot. Leaf spot diseases are generally fungal in nature and are cosmetic issues for many trees. However, since the Kwanzan cherry tree is not very hardy anyway, these diseases can create a serious problem over time if they are left untreated.
Kwanzan cherry trees are susceptible to verticillium wilt, a fungal infection that destroys the vascular system of the tree. If your tree appears to be wilting even in the presence of adequate water and cutting a small sliver in the bark reveals an olive-green stain in the wood, then your tree has verticillium. If you do not see a green stain, the tree may have conventional root rot that can destroy the roots of your cherry tree but is not usually contagious.
Kwanzan cherry trees are susceptible to many insect diseases. Aphids are small, oval green insects that ooze "honeydew," a sweet substance that invites secondary infections of mold and powdery mildew. Scale insects can also cause this problem. Spider mites can be difficult to see, but you will notice wilting and you may spot small webs in the crooks of leaf stems and branches. Large, webbed "tents" indicate the presence of tent caterpillars, which can defoliate a tree if they are not removed. All of these insect infections can be treated, but left unchecked they may destroy the health of the tree.
Preventing Kwanzan Cherry Tree Disease
Most of these diseases can be prevented by making sure your Kwanzan cherry tree is located in well-drained soil that is in full sun and that you are watering and pruning properly. Only water in early morning, and do not do so unless there is a drought. The tree should be pruned or the plants around it should be pruned so that sunlight can reach the center of the tree. Also, treat your Kwanzan cherry with horticultural oil or a diluted spray of liquid dish soap on both the tops and bottoms of leaves to prevent insect infestations.
Treating Kwanzan Cherry Diseases
If you notice that your Kwanzan cherry tree is looking under the weather, you will need to act fast to save the tree. Remove all affected foliage using sterile pruning techniques, and dispose of the plant debris in a sealed bag rather than allowing it to fall on the ground. Check for verticillium wilt if the tree appears to need water even though it has plenty. If you see the dark green stain in the wood, then you will need to remove the tree as quickly as possible to prevent the infection from spreading. However, if it has regular root rot, you may be able to save the tree if you improve drainage in the area and fertilize the tree. Insect infections can be remedied with pesticides or by the application of horticultural oils to the upper and lower parts of the tree, as well as sterile pruning and removal of any parts of the tree that have developed powdery mildew or mold infections.