Vineyard sanitation.
By changing or modifying environment, immunity can be secured from many of the pests of the grape and damage may be reduced with most if not all. Cultivation, as has been noted under several insect pests and one or two of the diseases of the grape, is an effective method of eliminating grape pests. In the case of insects, it destroys the insects themselves and the hibernating places as well. The vineyard should never be kept in sod, but always under thorough and frequent cultivation. Vineyard sanitation is greatly improved, also, if cover-crops which remain green during the winter are planted after the last cultivation. Cultivation should usually be preceded by deep plowing in the fall or spring to turn under fallen leaves and weeds or grass in which hibernating insects may pass the winter.
The surroundings of the vineyard should be looked after. Fence-rows and waste lands which cannot be cultivated may often be burned over to destroy the hibernating places of grape insects. As a rule, it is unwise to plant the bramble berries or even strawberries in vineyards, or adjoining vineyards, since these plants afford hibernating places and food plants for some of the grape insects, especially the destructive leaf-hopper. Lastly, precaution should be taken by destroying all wild grape-vines near vineyards, as these frequently harbor insects and diseases, the flea-beetle finding the wild grape-vine almost a necessity to its existence.
Spraying.
Definite rules cannot be laid down for spraying vineyards the country over. The literature on this subject is plentiful in any state in which grapes are largely grown, within the reach of the grape-grower, and is not difficult to understand once it is in hand. Every grape-grower should secure and study the publications of the state experiment stations having to do with the control of insects and diseases.
The number of applications and the sprays to be used vary greatly in different parts of America. On the Pacific slope the only application yearly required in most vineyard regions is dusting with flowers of sulfur for powdery-mildew. Several other pests may, however, from year to year, or in one locality or another, require special treatment. In the grape regions of New York, many grape-growers do not spray at all, but these are usually slovens or procrastinators whose profits are small and uncertain. In the grape regions of the northeastern states, orderly vineyardists spray at least once with bordeaux mixture (4–4–50) in which is put three pounds of arsenate of lead, no matter how few insects and fungi are present. This treatment is given soon after the blossoms fall. In more southern regions it may be necessary to make a similar treatment soon after the first leaves appear, again after the blossoms fall and every two weeks thereafter until the grapes begin to turn in color, making as many as four, five or even six applications in all. To these regular applications of bordeaux mixture and arsenate of lead, contact insecticides, as some of the nicotine preparations, may have to be added; or, for special purposes as specified in discussing the several pests, cheap molasses is added. It is doubtful, however, whether the grape can be grown with commercial success where insects and fungi prevail and are so pestiferous as to require annually more than two or three applications of spraying mixtures.
Plate XVIII.—Herbert (×2/3).