Manual of American grape-growing

by U. P. Hedrick

In eastern America, especially in the Chautauqua grape-belt, grape-growers not infrequently lose a large part of the crop by the premature falling of the grapes from the stems. The trouble is an ancient one and is designated as "shelling" or "rattling." This premature dropping usually begins at the end of a cluster, and clusters farthest from the trunk are earliest affected. When vineyards suffer badly from this shelling, the vines often take on a sickly appearance, the foliage falling off in color and the outer margins of the leaves drying up more or less. The fallen fruit has an insipid taste and is, of course, worthless even if it could be harvested.

The cause of the trouble is not known. Grapes may "rattle" on high land or low land, on poor soil or rich soil, on heavy or light soil. A vineyard may be affected one year and not the next. Grape-growers usually attribute the trouble to faulty nutrition, but applications of fertilizers have not proved a preventive. Old and well-established vineyards seem freer from the trouble than new and poorly established plantings. The most reasonable theory as to the cause of shelling is that it comes from faulty nutrition of the vine, but the conditions so affecting the nutrition are not yet satisfactorily determined.

Diseases of minor importance.

Ripe-rot or bitter-rot (Glomerella rufomaculans) is a disease due to the same fungus causing the bitter-rot of the apple. As the name indicates, the disease usually appears on the fruit at ripening time and under favorable conditions continues after the grapes are picked. It may also attack the leaves and stems. The first indication of the fungus is the appearance of reddish-brown spots which spread and eventually cover the whole fruit. The berries do not shrivel, but the rotted surface becomes dotted with pustules in which the spores are borne. It is hard to tell how much damage this disease does, but it is not usually great and the late applications of bordeaux mixture for black-rot or powdery-mildew are very effective in controlling it.

Crown-gall, now known to be a bacterial disease which causes knots or galls on the roots of various wild and cultivated plants, sometimes attacks grape roots or even the vines above ground. Occasionally, the disease is rather serious, but it is not often to be reckoned with in the vineyard regions of America. Fungicides are useless in combating the disease and all that can be done is to exercise great care in planting infected stock. It is doubtful whether crown-gall ever seriously injures vines in northern regions, although it may occasionally do so in the South.

In California there is a somewhat mysterious disease known as "Anaheim disease," because of its having first made its appearance in the vicinity of Anaheim. As near as can be learned, the disease first appeared in 1884 and then spread rapidly from forty to fifty miles from the point where it began its ravages, causing direct and indirect loss of many millions of dollars, and leading to the abandonment of grape-growing in some parts of southern California. Fortunately, in recent years the Anaheim disease is less aggressive but still does more or less damage. The nature and the treatment of this disease are not as yet fully determined, although several experimenters are studying the trouble. Californians whose vineyards suffer from this disease should apply to the experiment station at Berkeley for the latest information in regard to it.

Coulure is another trouble of the vine in California of which little is yet known, either as to cause or treatment. The term signifies the failure of the fruit to set or to remain on the clusters. The trouble occurs in varying degrees from the loss of a few berries to the complete shelling of the fruit from the stem. It is worse in some localities than others and in some varieties than others. Various causes have been assigned to the disease, chief of which, and most probable, are unfavorable climatic conditions.

Control of Insects and Diseases

From the number of insects and diseases found on the grape, it would seem that, literally, "pestilence walketh in darkness and destruction wasteth at noonday" in the vineyards of the country. But not many of the ills that grape-flesh is heir to are ever found in one region, and the vineyard is seldom attacked by many diseases or insects in a single season. There was a time, as we have said before, when grape-growers were so beset by pests which they could not control, that viticulture was one of the most uncertain fields in agriculture. But one brilliant discovery after another has brought the pests of the grape under the hand of man until now there are but few that need cause much expense in treatment or worry as to the outcome.

Plants cannot be attacked by diseases unless infection is permitted. It follows that by proper sanitation most of the insect pests of the vine can be kept out of the vineyard.