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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.
To dispose of citrus debris it should either be heated to a minimum of 180 °F for two hours, incinerated, buried in a landfill, or fed to livestock. Plant trash should be moved with caution if at all to avoid spreading the infectious ascospores. Any trees that are infected with citrus black spot should be removed from the grove and disposed of.
This disease affects strawberry plant foliage causing purple spots ⅛ to ¼ inches 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.
As the disease progresses, the mycelium often becomes dotted with minute black points (cleistothecia), which are the sexual fruiting bodies of the fungus. [3] The fungus does not kill the host plant as it requires the hosts' water and nutrients to grow. It settles on foliage and gradually slows the host growth process.
The initial symptoms appear as small, dispersed water-soaked spots on the back of the sunflower head. As the spots expand, mycelial growth expands into parenchyma cells, further killing cells within the head. Later stages of disease have external masses of mycelium among clumps of black sporangia, dispersing spores abiotically, and by birds.
Small black dots may form beneath the epidermis of the lower stem and in the taproot, giving the stems and roots a charcoal-sprinkled appearance. [8] When the epidermis is removed, small and black microsclerotia (a sign of the disease) may be so numerous that they give a greyish-black tint to the plant tissue. [ 8 ]
People can observe P. infestans produce dark green, then brown then black spots on the surface of potato leaves and stems, often near the tips or edges, where water or dew collects. [9] The sporangia and sporangiophores appear white on the lower surface of the foliage. As for tuber blight, the white mycelium often shows on the tubers' surface. [10]
When the chlamydospores first infect the plant, they give rise to the mycelium, or hyphae network, which then lead to further spore infection. This gives rise to the black rot that is seen. If the infection is seen out in the field, the chlamydospores will over winter in the dead debris of the plants or in the soil. [5]