well down in the soil and there is little danger of injuring them in
deep tillage. The depth of plowing and cultivating should be varied
somewhat from season to season to avoid the formation of a plow-sole.
In some regions plowing and cultivating may be made a means of
combating insects and fungi, and this regulates the depth of tillage.
Thus, in the Chautauqua grape-belt of western New York, the pupa of
the root-worm, a scourge of the grape in this region, is thrown out
and destroyed by the grape-hoe just as it is about ready to emerge as
an adult to lay its eggs on the vines. In all regions, leaves and
mummied grapes bearing countless myriads of spores of the mildews,
black-rot and other fungi are interned by the plow and cannot scatter
disease.

The time in the season to stop tillage depends on the locality, the
season and the variety. It is a good rule to cease cultivation a few
weeks before the grapes attain full size and begin to color, for by
this time they will have weighted down the vines so that fruit and
foliage will be in the way of the cultivator. In the North,
cultivation ceases in the ordinary season about the first of August,
earlier the farther south. Rank-growing sorts, as Concord or Clinton,
do not need to be cultivated as late as those of smaller growth and
scantier foliage, as Delaware or Diamond. The cover-crop seed is
covered the last time over with the cultivator. Plate IV shows a
well-tilled vineyard of Concords.

IRRIGATION

The grape, as a rule, withstands drought very well, several species
growing wild on the desert's edge. Even in the semi-arid regions of
the far West, where other fruits must always be irrigated, the grape
often grows well without artificial watering. Irrigation is practiced
in vineyards in the United States only on the Pacific slope and here
the practice is not as general as with other fruit crops. Whether the
grape shall be grown under irrigation or not is a local and often an
individual question answered with regard to several conditions; as the
local rainfall, the depth and character of the soil, the cost of water
and ease of irrigation. These conditions are all correlated and make
about the most complex and difficult problem the growers of grapes in
semi-arid regions have to solve. As long, however, as the grape-grower
can grow fairly vigorous vines and harvest a fairly bountiful crop by
natural rainfall, he should not irrigate; for, even though the crop
offsets