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Typical viral disease of alfalfa. The symptom often appears in spring and autumn, especially around the first cutting. Most individuals are infected at the second year from seeding in the warm regions. The symptoms are at first yellow mosaic or green mosaic in a young leaf. When the disease advances, the symptoms appear such as chlorosis, rugose, rosette, etc. The virus is transmitted mainly by sucking of the aphids and the sap transmitting by machine cutting and the seed transmitting, etc. There are a lot of strains in the causal virus and the symptom is slightly different according to the strains. At least more than 73 genus and 220 kinds of plants are infected by inoculation of the virus. |
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Spot-causing bacterial disease mainly occurring in leaf. The lesions are at first minute water-soaked round spots and then become to faint brown with dark brown border ones of 2-3 mm in diameter. A yellow halo is formed in the surroundings of the lesion and the infected leaf shows malformation. |
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Fungal disease occurring from summer to autumn and causing large damage in the warm regions. It occurs in the leaf, stalk and petiole and produces yellowish brown, spindle shaped lesions sinking a little with black mold (setae) in the center part. The upper part of the lesion often withers and the entire plant is killed in results. The causal organism can infect clovers, too. |
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Spot-causing fungal disease occurring a lot in cool and wet conditions. It occurs in the leaves, petioles and stalks. The lesions are at first tea brown spots such as needle-points in the leaf and become round ones of 1-2 mm. Dark brown perithecia like warty are produced in the center part of the lesion later and this part becomes like jelly at wet conditions. The leaf turns to yellowish brown and defoliates easily when occurring severely. The causal organism is different from leaf spot fungi of clovers. |
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Fungal disease which causes plant withering and death. Blackish brown lesion of several centimeters surrounds the stalk and extends from the ground side part. The surface of the lesion are somehow rough and sinks slightly. Most lesions stay in the cortex and the root generally has no lesion. Reddish brown microsclerotia are formed in the lesion and the entire ground part will become yellow before long. The host range of the causal organism is wide and it shows pathogenicity in clover, trefoil, soybean and azuki-bean. |
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Fungal disease occurring in leaf. It often begins to occur from the rim of young leaves and the lesions become dark green and irregular shaped. Later the lesions turn to yellowish and gray molds which is zoosporangia of the causal organism are produced at the backside of the leaf. Then the lesion part shrinks, turns to brown and the entire leaf withers. |
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Fungal disease to infect the entire upper-ground part. It occurs at the ground side of the plant which grows thickly and water-soaked small spots is formed in the leaf and stalk. Then, the whole plants soften and collapse to brown. Gray molds grow bristly in the rotted part. It occurs severely at the high temperature and humidity. |
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Spot-causing fungal disease occurring in the cool regions. In the beginning, young leaves are infected, but the entire upper-ground parts such as petiole, etc. are diseased later. The light brown, small lesions of 1-2 mm in diameter and with faint halo in the surroundings are produced in the early spring. They expand before long and become grayish white, round ones with blackish brown borders. The leaf withers finally. The disease spreads again in autumn and occurs abundantly in the cool year with frequent rains. Black small grains, the perithecia of the causal organism, are formed on the old lesion. The ascospores are discharged here and spread. The species of the causal organism is different from that of pepper spot of clovers.
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Typical rust disease. The uredinia are reddish brown to brown, small and round and scatter on the surface of the leaf and stalk. The epidermis tears when maturing and they disperses urediniospores. The telia becomes dark brown. The alternate host of the causal organism has not been confirmed in Japan yet. |
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Important fungal disease which causes plant death occurring in cool and wet regions. The small spots appears at first and then the leaf and stalk turn to yellow and wither. The disease progresses gradually under the snowfall. The stem, leaf and root rot to ash white according to increase of the temperature after snow-melting in the spring of next year. White and fluffy hyphae are produced on the surface of the withering plant and large black sclerotia of irregular types and about 8-10mm in size are produced before long. They germinate in autumn and produce light brown stroma of 3-8 mm in diameter. The ascospores spread from the stroma and the infection happens again. The host range of the causal organism is wide including clovers and vetches. |
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