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.

Since the disease is carried through the winter in mummied fruits and
diseased wood, the desirability of destroying these