Category:Diseases

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List of diseases in PRGDB.

  Description
Aculops Lycopersici Russet mites are so small that a 14X hand lens is needed to see them. Because of their size, these mites are rarely noticed until plants are damaged. By this time, there may be hundreds of yellowish, conical-shaped mites on the green leaves immediately above the damaged bronzed leaves.
Alfaalfa Mosaic Typical leaf symptoms on plants with alfalfa mosaic include bright yellow blotches with some mottle. Leaves eventually develop a bronze discoloration. Internally, phloem tissue becomes necrotic, including the phloem in the roots. The disease usually causes plant death. One of the most striking symptoms is the necrotic rings and spots on the fruit. Some fruit may develop a solid brown necrosis over the surface.
Alternaria Stem Canker Symptoms of Alternaria stem canker appear on stems, leaves, and fruit. Dark brown to black cankers with concentric zonation occur on stems near the soil line or aboveground. Cankers enlarge, girdle the stem before harvest, and kill the plants. Vascular tissue about 2 inches above and below the cankers exhibit brown streaks. Dark brown to black areas of dead tissue between leaf veins are caused by a toxin produced by the fungus. Dark brown sunken lesions with characteristic concentric rings develop on green fruit either on plants or during transit.
Andean Potato Mottle virus yellow local lesions or blotches, mild or severe mottle some leaf malformation.
Andean Potato latent virus "the virus was latent in most isolate/cultivar combinations with primary infection but secondary infection commonly caused symptoms. Wild species infected with the different isolates normally reacted with symptoms with either type of infection. The main symptoms were mosaics, chlorotic netting of minor leaf veins and, with wild species, leaf deformation; the netting symptom was typical only with Caj. In infected cultivars growing in the field, an additional symptom, rugosity, sometimes also developed and environmental conditions at high altitude seemed to enhance symptom formation. Very severe symptoms were found in a cultivar jointly infected with APLV and Andean potato mottle virus. Transmission of APLV from an infected plant to its tubers was erratic."
Anthracnose Anthracnose of tomatoes is primarily a disease of ripe and overripe fruit. Depressed, circular lesions about 0.5 inch (1.2 cm) in diameter appear on ripe fruit. With age the lesions become tan and dotted with small black specks (microsclerotia). During moist weather, masses of salmon-colored spores may form on the lesion surface. Infection may also occur on stems, leaves, and roots. Root infections (called black dot root rot) become evident when fruit begin to ripen. Root lesions are brown and dotted with microsclerotia. The cortex of infected roots is often completely rotted.
Bacterial Blight Leaf lesions begin as light yellow spots. They expand and become brown and water-soaked with yellow halos. Affected tissue eventually turns black. Young leaves turn black and die quickly. Lesion expansion occurs slowly on older leaves. Affected leaves may also exhibit black streaks along midribs and veins. Leaves displaying this symptom may al be crinkled along the midvein or margin. Petioles and stems may be girdled by black lesions and the tissue beyond this point withers and dies. Tissue directly affected by syringomycin turns black and exhibits water-soaking while those that die as a result of girdling turn brown. Dead shoots bend, forming a shepherd's crook. Twigs that become woody before infection occurs have lesions comprised of black streaks that run lengthwise. Flower clusters often blight rapidly when infected and turn black. The rest of the inflorescence turns dark brown and limp.
Bacterial Canker "There are usually no symptoms of bacterial canker on seedlings; however, on young plants symptoms consist of poor growth and temporary wilting of branches. Lower leaves yellow and shrivel, but symptoms may not show until flowering. On mature plants there are two kinds of symptoms, those resulting from systemic infections (i.e., the bacteria enter the vasculature and invade much of the plant) and those resulting from secondary infections (i.e., the bacteria cause local infections of leaves, stem, and fruit).In systemic infections of mature plants, leaflets of the oldest leaves curl, yellow, wilt, and finally turn brown and collapse (known as firing). Sometimes, one side of a leaf is affected. Plants grow poorly and wilt. Pith of stems becomes yellow and later reddish brown, especially at the nodes, and has a mealy appearance. The pith may later become somewhat hollow. In advanced infections, cankers may or may not form at the nodes. Light and later dark streaks may develop on stems. Branches break off easily. Plants may die.In secondary infections, infection of the margins of leaves is common. Lesions are dark brown to almost black. Round to irregular spotting of leaves also occurs. Fruit may be spotted, especially near calyx. On fruit bacterial canker symptoms appear as yellow to brown spots, slightly raised, surrounded by a persistent white halo (""bird's eye spot""). Spots are usually about 0.125 inch (3 mm) in diameter. Vascular tissue under the calyx scar and leading to seeds that may be brown."
Bacterial Ring Rot Foliar symptoms of bacterial ring rot generally appear at mid-season or later. Yellow areas develop on leaf margins or between veins and later turn brown, giving the leaves a burned appearance. Plants with advanced symptoms show vascular discoloration and milky, viscous bacteria may be forced from cut stems. In tubers, symptoms may occur before harvest or in storage. Rot begins as a brown necrosis in the vascular ring and progresses to surface. Cracks may appear on surfaces of tubers, which are frequently nothing more than hollow shells.
Bacterial Speck Bacterial speck appears as dark brown to black lesions of various sizes and shapes on leaves, fruit, and stems. Tissue adjacent to the lesions is initially yellow. Leaf lesions are frequently concentrated near margins, causing extensive marginal necrosis (tissue death). Lesions on immature fruit are slightly raised and small, varying in size from tiny flecks to 0.125 inch (3 mm) in diameter and cause raised black spots on mature fruit. Fruit lesions are superficial, seldom penetrating more than a few cells deep.
Bacterial Spot Bacterial spot develops on seedlings and mature plants. On seedlings, infections may cause severe defoliation. On older plants, infections occur primarily on older leaves and appear as water-soaked areas. Leaf spots turn from yellow or light green to black or dark brown. Older spots are black, slightly raised, superficial and measure up to 0.3 inch (7.5 mm) in diameter. Larger leaf blotches may also occur, especially on the margins of leaves. Symptoms on immature fruit are at first slightly sunken and surrounded by a water-soaked halo, which soon disappears. Fruit spots enlarge, turn brown, and become scabby.
Bacterial Wilt (Arabidopsis) This disease occurs in scattered plants or groups of plants. The initial symptom is wilting of terminal leaves, followed in 2-3 days by a sudden and permanent wilt. Adventitious roots may develop on the main stems. Additional symptoms include vascular browning, water soaking of pith followed by browning, and in later stages browning of cortex near the soil line. Bacteria streaming can be seen when a freshly cut stem is suspended in water.
Beet cyst nematode Entire fields can be infested, or localised infection can appear as circular or oval areas where plant stand and growth are poor. Over time, the smaller areas of infestation will enlarge and spread. Beet cyst nematode can infect plants of all ages. Seedling attack can result in severe injury or even plant death. When older plants are attacked, less damage will occur. Above-ground symptoms consist of reduced stand, poor growth, stunting, yellowing and wilting Roots attacked by beet cyst nematode appear ?bearded? or ?whiskered? due to the excessive development of fibrous roots. Root vegetables will have smaller storage roots which may have abnormal swellings. The most evident sign of beet cyst nematode is the appearance of glistening white-yellow bodies about the size of a pin head attached to the fibrous roots
Black Dot silvery lesions on the tuber surface which result in a deterioration in skin quality. In addition to causing tuber blemish symptoms, C. coccodes also causes symptoms on stems and foliage, resulting in crop losses in some countries, and is implicated as a factor in the potato early dying disease complex.
Black Mold Blackmold is characterized by obvious lesions that appear on the surface of ripe fruit. Lesions are light to dark brown and vary from small flecks affecting only epidermal tissue to large, more or less circular, sunken lesions with decay extending into the carpel wall and often into the seed locule. During warm, humid weather the fungus may sporulate to form a black, velvetlike layer on the surface of the sunken lesions.
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Pages in category "Diseases"

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