Bark Diseases on Orange Trees
Originating from Asia, orange trees are now a staple in the United States economy. Orange trees are prone to many forms of fruit tree diseases, which can devastate a crop and its harvest capabilities. Viral, bacterial and fungal bark diseases can affect a citrus plant's bark, fruit and leaves, leaving the tree unable to produce. Several viral and fungal diseases in particular exhibit symptoms of bleeding, shelling, scaling and flaking of the bark.
Exocortis is an orange tree virus that is also known as "scaly butt." It leads to severe and giant cracks in the bark of the tree, causing the orange tree to split. The bark eventually flakes off and kills the citrus tree. Another symptom of exocortis is yellow blotches found on the tree's leaves, which eventually die and fall off.
Citrus Phytophthora Gummosis
Citrus Phytophthora gummosis is a highly contagious fungal infection of the orange tree. Cracks in the bark appear and sap from inside the tree oozes out, creating the appearance of bleeding bark. These cracks and splits in the bark of the orange tree will spread around the circumference of the tree, causing the bark to split, and eventually will take down the tree. Another symptom of this disease is a water-soaked soil line at the base of the citrus tree that exhibits a black to reddish color bark. Another characteristic of this disease is yellow, sparse foliage.
Also known as scaly bark disease, psorosis has been the most serious virus disease to occur in mature orange trees. Certain strains of psorosis are spread through seed while others are spread from early nursery buds infected with the disease. Typically prominent in sweet orange and tangerine trees, this disease can be devastating. The earliest symptom is scaling of the bark. As the disease spreads, the citrus tree slowly declines and becomes unproductive.