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Pyrenophora tritici-repentis and Drechslera tritici-repentis is a necrotrophic plant pathogen of fungal origin, phylum Ascomycota. [1] The pathogen causes a disease originally named yellow spot but now commonly called tan spot, yellow leaf spot, yellow leaf blotch or helminthosporiosis.
Puccinia thaliae is the causal agent of canna rust, a fungal disease of Canna. Symptoms include yellow to tan spots on the plant's leaves and stems. Initial disease symptoms will result in scattered sori (clustered sporangia), eventually covering the entirety of the leaf with coalescing postulates.
Small water-soaked lesions, maturing into sunken and brown spots with or without a yellow halo. May show concentric rings with purple margins. Necrotic tissue may fall out to appear shot-holed. Leaf spot on many plants and crops. Septoria: Small brown spots, that turns light tan to white in the centre. Leaf spot on many crops Bipolaris
Prunus necrotic ringspot virus (PNRSV) is a plant pathogenic virus causing ring spot diseases affecting species of the genus Prunus, as well as other species such as rose (Rosa spp.) and hops (Humulus lupulus). [1] [2] PNRSV is found worldwide due to easy transmission through plant propagation methods and infected seed. [3]
Prunus serotina, commonly called black cherry, [3] wild black cherry, rum cherry, [4] or mountain black cherry, [5] is a deciduous tree or shrub [4] in the rose family Rosaceae. Despite its common names, it is not very closely related to commonly cultivated cherries .
Infected leaves are filled with numerous black lesions that cover an obvious portion of the leaf. [5] These lesions first appear as small purple spots which turn red to brown and then black. Most spots are circular but can amalgamate to form large, irregular dead patches. [6] These spots tend to enlarge and separate from healthy tissue.
Leaves retain their yellow border from the initial chlorosis. Apothecia survive in the fallen plant debris over winter, releasing spores when the temperature is warm again. [ 5 ] The infection of Tar Spot is localized to the chlorotic areas on the leaves and is mostly a cosmetic issue, rather than an economically detrimental disease.
Stegophora ulmea is a foliar disease of elms commonly known as black spot of elm, twig blight, and elm leaf scab. [1] It is characterized by yellow spots that become black spots on the leaves. The pathogen is an ascomycete fungus native to North America. Stegophora ulmea is its teleomorph name. [2]