The Raisin Industry / A practical treatise on the raisin grapes, their history, culture and curing

by Gustavus A. Eisen

Sulphuring.

—Sulphuring the vines is now considered a most necessary operation, and without doing it well and in time no good crops can be relied upon. It is true that good crops of grapes are sometimes had without sulphuring, but this is only due to chance; the absence of mildew, and immunity from disease of unsulphured vines are rare, even in otherwise most perfectly kept vineyards.

The sulphuring consists in thoroughly dusting the growing vines, leaves, branches, flower buds and berries with powdered sulphur. The first sulphuring must be done when the grapevines leaf out in the spring, and, when the young shoots are about six inches long, it is about time to commence. Many growers sulphur only once, some go over their vines two times, but our most successful growers,—those who get the best and largest fruit crop of grapes and bunches,—sulphur in unfavorable seasons three or four times. The second sulphuring is done just before the blossoms open, and may even, provided the weather remains cool and windy, be done in the open blossoms with great benefit to the setting berries. Miss M. F. Austin of Fresno was the first to successfully sulphur in the open blossom, the result being very large crops. But not all have been as successful as she, and one of our most experienced vineyardists and raisin-growers, T. C. White, prefers to sulphur just before the blossom opens, as, in case of very warm weather when the sulphur is thrown on the blossom, the latter is apt to blast. We are therefore on the safe side if we sulphur just before the buds have opened, and after the grapes have set. But on cold, windy days when one of the cold electric northwest winds are sweeping down the valleys, sulphuring must be done whether the blossom is open or not, as it is just at this time the sulphur is required the most, in order to counteract the formation of the first stage of the powdery mildew. The vapor of the sulphur destroys the germs of the mildew, and thus prevents the latter from causing the grapes to fall off. After the grapes have fully set, no further sulphuring is required except in the case of heavy rains or in continued cloudy weather, when there is always danger that the mildew will reappear. If heavy rains should occur during the summer, a renewed sulphuring is always necessary or at least advisable, but in ordinary seasons no sulphuring is needed after the berries have set well, as the germs of the mildew are then sufficiently injured to not develop later in the season.

Sufficient sulphuring is always noticeable in the vineyard by its smell, and, when this smell is strong and pronounced, no further sulphuring is required. The sulphur is applied to the vines either by the “dredger” (or dust-can) or by a pair of sulphur bellows. The dredger is used when the vines are small, while the bellows are necessary to spread the sulphur evenly when the vines have reached a certain size. Many growers use, during the first sulphuring, small burlap bags filled with sulphur. The meshes of the burlaps are large enough to allow the sulphur to go through. The sulphur should be finely pulverized to be effective, and the sublimated French sulphur is by many considered the best. The cost of sulphuring varies according to the size of the vines, but is generally about three dollars per acre. Young vines under three years of age require little sulphuring, while older vines require a great deal. About ten tons of sulphur will be enough for 160 acres.

Tying Over.

—The tying over of the branches is another vineyard operation much used in the interior raisin districts, generally in the end of June or the middle of July. It consists in so bending and tying the long, straggling branches of the vine that they will shade the grapes hanging in the center. The long branch is bent, not in a direct line towards the center, as it would then expose too many of the lower grape bunches, but in a spiral direction round the vine. If there is any fear that the grapes will be exposed and sunburned, and the vines have not been properly summer pruned, the tying over is the only process by which great loss can be prevented and the grape crop saved. In tying over, no twine is used. The end of the long branch is twisted and fastened to other branches, and, when the grapes are ripe and the picking season comes, a single light pull will suffice to untie all and allow the grapes to be picked. Great care should be used in tying over, lest the lower branches become exposed and sunburned. Careless or inexperienced laborers will often accomplish a great deal of work and a great deal of harm in an incredibly short time. I have seen vineyards where more harm was done by tying over than by the sun and wind combined.

Covering the Vines.

—Instead of tying over, many vineyardists now cover the vines, and place the covers on the open center of the vine, in order that they may protect the grapes from exposure to the sun. This is done in June, several days before the hot spell is expected. The last week in June is the best time almost everywhere in California, as the vines are then open in the center, and any unusually hot weather would easily cause the grapes to sunburn. The process of covering is very simple. With a pair of shears the longest branches are clipped off and immediately placed on the open center. This is generally enough to prevent the exposed grapes in the center of the vine from being scalded. More than half a dozen branches will seldom be required, and at picking time these dry branches must first be thrown off, so as to give the picker access to the grapes. The covering of the vines is a better process than tying over, requiring less work and being more quickly performed. It is especially useful for old vines, as the grapes of young vines are principally exposed from the sides.

Thinning the Crop.

—The proper thinning of the crop should be done by pruning. If the proper amount of wood is left, no thinning out of the grapes is needed. If a few show-grapes or extra large raisins are needed for exhibiting purposes, they can be produced by a judicious cutting of the majority of the grapes from any single bunch. If the free half of the bunch is cut off, the part that is left will produce very large grapes. This operation is, however, never likely to enter as a regular vineyard operation in our vineyards, as with us labor is too scarce. The object of our raisin industry is to produce cheap medium-sized raisins of good quality, to be used by the masses of the people, instead of a smaller quantity of very large grapes, which could only be used by the rich.