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The most common cause of bacterial leaf spots are by bacteria in the genera Pseudomonas and Xanthomonas. For example, Pseudomonas syringae pv. tabaci is known to cause angular leaf spots of cucumber, Pseudomonas syringae pv. phaseolicola to cause bean leaf spot and Xanthomonas campestris pv. phaseoli, angular leaf spot of cotton. [7]
Most commonly Cephaleuros virescens is identified by the leaf spots it causes. Theses leaf spots are an orange-brown rust in color and usually occur entirely on the upper leaf surface, although leaf spots on the undersides of infected leaves have been reported. The spots are fuzzy in texture and approximately 2 cm (0.8 in) in diameter. [2]
This disease affects strawberry plant foliage causing purple spots 1 ⁄ 8 to 1 ⁄ 4 in (3.2 to 6.4 mm) in diameter across on the upper side of the leaves. [3] At first, the whole spot is purple but as the disease matures the center of the leaf spots on older leaves become tan or gray, then almost white. Lesions on younger leaves remain light ...
Tobacco mosaic and bacterial leaf spot are two common issues. "The tobacco mosaic virus is transmitted from other plants nearby, mites, nematodes, aphids, and thrips," says Langelo.
Plants can drop 50–100% of their foliage. BLS can also affect the stems of plants, leading to elongated, raised, light-brown cankers, less than .25 inch long. (5) Defoliation occurs more commonly in pepper plants than tomatoes, so tomato plants with bacterial leaf spot often have a scorched appearance due to their diseased leaves. [2] [5]
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] A microscopic sign of the pathogen are the stroma, mats of hyphae found in the lesions. [2] These lesions can cause senescence of leaves but are mostly of cosmetic importance.
A raspberry leaf spot infection initially causes dark green circular spots on the upper side of young leaves, which will eventually turn tan or gray. [3] These spots are typically 1–2 millimetres (0.039–0.079 in) in diameter, but can get as big as 4–6 millimetres (0.16–0.24 in). [4]
Stemphylium solani is a plant pathogen fungus in the phylum Ascomycota. It is the causal pathogen for grey leaf spot in tomatoes and leaf blight in alliums and cotton, though a wide range of additional species can serve as hosts. Symptoms include white spots on leaves and stems that progress to sunken red or purple lesions and finally leaf ...