Cryptomeria Yoshino Diseases

Yoshino is a cultivar of Cryptomeria japonica, or Japanese cedar. It grows well in hardiness zones 6 to 8 and grows well in urban areas, even in spots like parking lots. With a height of 30 to 40 feet and a pyramidal shape to its crown, it makes a beautiful landscaping feature in areas large enough for its size. The Yoshino cultivar experiences less discoloration of its needles in the winter than other trees of the species. It is generally resistant to diseases, but may be affected by leaf spot and leaf blight. Mites and Cryptomeria scale are pests that can also cause problems.

According to the University of Missouri Commercial Agriculture Extension, leaf spot is a disease that can affect any tree or shrub. It is primarily caused by fungus, but bacteria may also cause the problem. It is a cosmetic problem that won’t seriously harm the tree and it is difficult to control. Symptoms are brown spots on the needles that may have black dots in the center. Needles will eventually turn brown and fall off. Removing and disposing of infected needles, keeping trees healthy and foliage dry can help control the disease. Fungicides can help, but treatments should start before symptoms are seen. Cryptomeria Yoshino is rarely affected by this disease, however.

Leaf blight, or needle blight, is also caused by a fungus. In Japanese cedars, the fungus is Cercospora sequiae. It will appear as brown needles on the interior foliage. Spraying trees with fungicide and keeping the foliage dry can help prevent the disease. In Japan, where the fungus was first seen in 1910, it has been controlled by using fungicides in nurseries.

According to the United States National Arboretum, Cryptomeria red mites can cause extensive damage to the needles of Japanese cedar and are active in cool weather. Symptoms are yellow stippling on the needles, which then turn brown before falling off, and possibly a silky webbing. The best way to check for mites is to tap a small branch while holding a white sheet of paper under it. Moving red or black spots on the paper are mites. If there are more than 20, the mites should be controlled with miticide. Check that the label says it can be used on Cryptomeria. Oil is used to control mites on other trees, but it will damage Cryptomeria needles.

Cryptomeria scale is a type of insect that sucks juice from plants, according to the University of Maryland Cooperative Extension. Symptoms include yellow spots on needles, chlorosis and possibly dieback with high populations. Despite the name, these pests rarely infest Cryptomeria. They are more likely to be found on cedars in the Cedrus genus, firs, and cypress.