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Black spot leaf disease is a physiological plant disorder that affects some grape varieties such as Concord.It is essentially a potassium deficiency that causes the leaves on a vine to turn purple and eventually black as chlorophyll is lost.
The infection in leaves usually remains latent until the leaves drop, but leaf spots may be found on older leaves. [22] [30] The leaf lesions usually produce ascospores, but sometimes produce pycnidia. [13] [26] [31] These pycnidia release pycnidiospores (conidia) in a gelatinous mass. [32]
Leaf spots can vary in size, shape, and color depending on the age and type of the cause or pathogen. Plants, shrubs and trees are weakened by the spots on the leaves as they reduce available foliar space for photosynthesis. Other forms of leaf spot diseases include leaf rust, downy mildew and blights. [4]
The black spots can become about 5 millimeters in diameter. [1] As the season continues, the tissue around the original spot may become necrotic. [4] In severe cases of the disease there is premature shedding of leaves, blight of young leaves and shoots, and complete defoliation early in the fall. [1] Fruits that are infected become crumpled. [1]
The white and yellow flowered “Singapore" cultivar, also from the United States, usually holds its leaves all year round in Hawaii. [25] Coleosporium plumeriae, known as plumeria rust or frangipani rust, is a fungus which attacks young leaves of P. rubra. It causes a brownish or orange powdery coating or blistering of leaves.
Hymenosporum flavum is a semi-deciduous tree up to 25 m (82 ft) high and a trunk diameter to 45 cm (18 in). [4] [5] The obovate leaves are simple, alternate, glossy green above and lighter below.
It is responsible for the black spot disease on papaya trees. It affects generally leaves and fruits at any time. It affects generally leaves and fruits at any time. Sporodochia of Asperisporium caricae was growing under side of leaf, dark blackish brown to black, stroma well-developed, erumpent .
The black spots are circular with a perforated edge, and reach a diameter of 14 mm (1 ⁄ 2 inch). Badly affected plants, however, will not show the circular patterning, as they combine to cause a large, black mass. The common treatment of the disease is to remove the affected leaves and spray with antifungal solutions.