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In late spring, chlorotic spots appear on tree leaves. These develop into brown-black lesions, retaining the yellow border. [4] The lesions continue to grow, and by the end of summer form leaf spots that look like tar. [2] The spot can grow up to 1.5 inches (4 cm) in diameter. [4]
Cronartium ribicola is a species of rust fungus in the family Cronartiaceae that causes the disease white pine blister rust. Other names include: Rouille vésiculeuse du pin blanc (French), white pine Blasenrost (German), moho ampolla del pino blanco (Spanish). [2]
The symptoms give the disease its name. The first signs of infection that can be seen are yellow and brown spots that develop on the living needles, [7] [8] which soon turn red. This infection starts on the base of the crown on older needles, which then turn a brownish red at the tip, while the rest of the needle remains green. [9]
Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as the signs of the causal pathogen are quite distinctive. Infected plants display white powdery spots on the leaves and stems. [1]
Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves. [2]
Edema, (also spelled oedema, and named from the analogous disorder in humans and other animals), is a disorder in plants caused by the build-up of water in plant tissues faster than the leaves can transpire. [1] [2] The excess fluid bursts the cell membranes, which can appear as blistery growths, red spots, or small white 'crystals'. [3]
The most infected needles are prematurely shed by December. Because the infected needles are within the interior of the tree, the newer needles on the outer surface of the pines are flushed green and resistant to the disease. However, the premature shedding of needles in the interior can extend outwards leading to a loss in overall growth.
The species is traditionally known as Meria laricis.Meria was first described by Jean Paul Vuillemin (Vuill.) in France in 1896. [1] DNA analysis in the 1990s indicated its closest ancestor was the Rhabdocline genus, with the similarity significant enough for the genera of Meria, Hartigiella, and Rhabdocline to be combined as synonyms, with Rhabdocline chosen as the name of the merged genus.