The grape is ravaged by four or five fungous diseases in America, unless the utmost vigilance is exercised to keep the parasites in check. Happily for commercial viticulture, there are regions, as we have seen in the description of grape regions in Chapter I, so fortunate in their freedom from fungous diseases that there is little uncertainty in grape-growing and but small expense in controlling diseases. Also modern science has discovered the life history of all the important diseases and devised fairly effective means of combating them. All of the fungous parasites of the grape in America are indigenous, having long subsisted on wild vines. They are, therefore, all widely distributed, and as cultivation has presented to them great numbers of grape plants in continuous areas, the diseases have increased rapidly in intensity, at times have swept like wildfire through grape regions devastating and utterly ruining great areas of vines. Means, however, are now at hand in remedial and preventive treatment, which, while because of cost may not permit the grapes to be grown profitably in all parts of America, do permit their culture for home use in practically all agricultural districts in the country. [Illustration: PLATE XVII.--Empire State (x2/3).] _Black-rot._ [Illustration: FIG. 44. Work of black-rot of the grape.] This is the most widely distributed and the most destructive fungous disease of the grape in the region east of the Rocky Mountains. Fortunately, it is unknown on the Pacific coast. The disease is caused by a parasitic fungus (_Guignardia Bidwellii_) which gains entrance to the grape plant by means of minute spores distributed chiefly by wind and rain. Black-rot passes the winter in mummied grapes, on dead tendrils or on small, dead areas on the canes. In the spring, the fungus spreads from these spots to the leaves and forms brown leaf spots about a fourth of an inch in diameter, or oblong, black spots on the shoots, leaves, petioles and tendrils. Later the disease spreads to the fruits, not usually attracting attention until the berries are at least half grown. Soon after the ravages of the fungus become apparent on the berries, the fruits turn black, shrivel and become covered with minute black pustules which contain the summer-spores. Figure 44 shows the work of black-rot. In the winter and spring, another form called the winter- or resting-spore is produced upon these old, shriveled, mummied berries, and these carry the disease over from one season to another.