If you own a flowering cherry tree in North America, you are not alone. These trees are prized for their white, to pink, to bright-pink flower blooms that they have. But, these trees are susceptible to infection from a variety of diseases, which, if severe, can kill the tree. The most common and threatening diseases are leaf spot, black knot, powder mildew, witches broom and leaf rot. All of these diseases are caused by fungal growth.
Leaf spot occurs as off-colored spots on the top of leaves. Cherry tree leaves are green, and so leaf spot will appear as yellow to yellowish-brown discolorations. Young branches and twigs can also be affected, with similar discoloration. Leaf spot arises in humid weather, but when conditions become moist, mold spores will appear on the underside of infected leaves. When these leaves fall to the ground, the spores leach into the ground when rained upon, continuing the cycle. Fungicide, which should be bought after consulting a local nursery, is the main treatment. To help the treatment along, infected leaves on the tree and ground should be destroyed.
When burrs, bumps or non-uniform shapes appear on branches, twigs and stems, it is likely that black knot is present. The growth can occur on the bark or the wood below the surface. Eventually, the growth will create cracks in the bark surface. While infected areas of the tree may live for several seasons, the tree will eventually die. Fungicides can be used, after nursery consultation, but it is necessary to remove infected parts.
Powder mildew appears as a whitish, powdery substance on leaves, stems and twigs. Severely infected leaves will become deformed. The powdery substance is a fungus, which water will wash off the leaves, into the ground, where it will leach into the tree's root system. Fungicide is the main treatment. Infected leaves should be removed, raked-up and destroyed.
Witches broom, which occurs as branch deformity, can affect flowering cherry trees. While the branches of a healthy cherry tree will grow uniformly, a branch with witches broom will grow at an angle different from the others. The main treatment for witches broom is pruning.
Leaf and Fruit Rot
When infected with leaf rot, a leaf will show circular holes in its body. Fruit and other parts of the tree can be infected as well, and an infected cherry fruit will show circular holes as well. To differentiate rot from insect damage, look for powdery, mildew-like, materials around the hole. Severely infected leaves and fruit will shrivel and fall from the tree. Tree parts infected with rot contain fungus spores, which can be leached into the ground by rain.
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