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Show r T MOSAIC DISEASE ATTACKS CUCUMBERS J Cucumber Mosaic Disease Produced by Transferring to a Healthy Plant Aphids From a Mosaic-Disease Plant Note Warty and Mottled Fruits. A now disease of cucumbers, known as the mosaic disease, has appeared during the past few years in commercial commer-cial greenhouses and in fields where cucumbers are grown for pickling purposes. pur-poses. Tho disease lias been known longest and is now most widespread and severe in the middle West, where the industry of growing cucumbers for pickling is centered, particularly in the states of Michigan, Wisconsin, Indiana, In-diana, Illinois and Minnesota. Recent Investigations of the disease have resulted re-sulted in the discovery of its nature, that it Is closely related to mosaic diseases dis-eases of other plants, and the present Indications nre that it can be controlled con-trolled by the introduction of sanitary measures and insect-control methods. Further experiments with control measures are being carried out. Appearance of Diseased Plants. The mosaic disease is commonly known in Michigan, Indiana and Wisconsin Wis-consin as "white pickle." In Minne- warty condition of the fruits, which often appear on cucumbers not more than an inch or two long, render them unlit for pickling purposes, so that in addition to the great reduction in yield caused by the disease, many, if not all, of the fruits produced by diseased vines are unmarketable. In the greenhouse the disease is quite similar in its principal symptoms, to those found in the field, the princi-, pal differences being that the disease appears to be more virulent, many of the plants wilting and dying. Nature of the Disease. The mosaic disease belongs to the same class as the mosaic diseases of tobacco, potato, tomato, poke weed and other plants, which have been known for some time. The exact cause of this class of trouble has not been discovered, dis-covered, but it is considered to be what Is known as the filterable virus, an agent of infection which is so finely di- IS-1" -ymi.yyyyy. vftilraSbwI-w.y.yww.y -y-3a.. Plant in a Field Badly Affected by Mosaic Disease Lead Pencil Shows Relative Size of Plant Note Runners Very Much Dwarfed, With Small, Wrinkled Leaves, Also Very Warty Fruit. sota it is commonly called "nubbins." The disease is characterized in the field by definite plant, fruit and leaf symptoms. When plants are attacked while very young, they nre markedly dwarfed by the action of the disease, growth is slow, the runners are very much shortened, the leaves are correspondingly corre-spondingly reduced in sse, the plants blossom sparingly, and the amount of fruit is very much reduced. When older old-er plants become diseased the principal visible effects are on the subsequent growth of vines and fruit, the vine tips and leaves being dwarfed and mottled and the fruit malformed as described elsewhere. The leaves of diseased plants are dwarfed, often curled and wrinkled, and usually have a mosaic or marbled appearance in which areas of light and dark green alternate. In some cases the leaves brown and die back from the tip. The fruits are very conspicuously affected, af-fected, being dwarfed, more or less mottled mot-tled or blotched with areas of darker green on a background of light green, greenish yellow, or almost white. In the most decided cases the green areas are raised and appear as definite warts or protuberances, sometimes of considerable consid-erable size, and the fruits take on many abnormal shapes. In some cases the fruits are almost white, hence the name "white pickle." This name probably prob-ably is due to a confusion of this diseased dis-eased condition with the white or albino al-bino plants which typically bear white-colored white-colored pickles, and which have been known to occur occasionally in fields for mauv years. The discoloration and vided that It will pass through a porcelain por-celain filter and still retain its ability to reproduce the disease when injected into healthy plants. The sap or juice of any portion of a diseased vine, if in jected into n healthy vine, will produce pro-duce the disease. The period of incubation, incu-bation, that is, the time which elapses from the inoculation of the vine to the first visible symptoms of the disease, in; the greenhouse is from seven to fourteen days, while in the field it is usually fourteen to twenty-five days. The agencies of transmission of the disease from diseased to healthy plants are doubtless many. It has been definitely defi-nitely proved that plant lice transferred trans-ferred from diseased to healthy plants will carry the disease. Control Measures. Judging from the nature of the disease dis-ease and from the preliminary experiments experi-ments thus far tarried out, the remedial remedi-al measures indicated by our present knowledge are (1) the eradication or control of insect pests which act as carriers of the disease, and (2) the application of sanitary measures to eliminate the sources of infection. To be most effective, these methods must be carried out by all the farmers of a community. Rigid insect control measures should be started as soon as the plants are up and continued throughout the season, sea-son, especially previous to the beginning begin-ning of picking, and all mosaic diseased di-seased plants pulled end destroyed, as well as plants with which they have come in contact. |