This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
The disease known as grape rot has prevailed to an unusual extent the past two or three seasons in many parts of Ohio and several of the adjacent States. From what I have seen and learned I believe that the crop of not less than a thousand acres of vineyards, or one-eighth of the aggregate of our State, was destroyed by it the past season.
I wish to enlist the sympathies of Editor Meehan and a goodly number of the readers of the Monthly in behalf of thousands of our perplexed grape growers, and to ask them to co-operate with us in observing facts and testing experiments that may assist in solving the problem as to the cause of the rot and the means of its prevention; for we are not willing to accept the opinion that these matters are past finding out.
In order to prepare the way for further advance, and to give the public the benefit of what has been already learned, I append here a brief summary of facts and observations, some of which are old and others have been elicited at recent meetings of our State and county horticultural societies in discussions on this subject.
Grape rot has prevailed, more or less, for about thirty years in southern Ohio and parts adjacent, affecting chiefly the Catawba variety; but of late years it has prevailed in nearly all parts of the State, though less along the lake shore and on the islands than elsewhere, and has affected the Concord, Ives, Hartford and Iona varieties, as well as the Catawba, while the Delaware and a few others escape the rot but are liable to mildew. The disease attacks the fruit suddenly, from the time it is one-third grown until of full size, sometimes destroying the whole crop, but usually leaving a few good clusters, or some sound berries on clusters mostly destroyed.
Vines of thrifty growth and on rich and moist soils are most liable to the disease, and such as have been in bearing six to ten years are more liable than young vines; in fact the disease seldom appears until after three or four years of bearing. Heavy rains in June and July are almost certain to bring the rot, especially if accompanied by hot and "muggy " weather, low barometer and little wind; and soils which allow the water to soak in deeply are worse than where most of it runs off quickly. Sheltered positions are also worse than those fully exposed to winds. Hence vineyards on elevated positions and hard clayey slopes are least liable to the disease.
Vines trained against buildings, especially on the east and south sides, where most sheltered from rain and dew, are not affected with rot; and vines growing on trees where the fruit is largely sheltered from above but open to free circulation of air generally escape disease.
A coping of two wide boards, in roof form, on top of the trellis, will generally protect the fruit from rot. Some advantage is also secured by training the vines so that most of the young shoots and foliage shall be on the upper wires of the trellis and the fruit on those below, taking pains to remove surplus leaves from among the fruit to give free circulation of air.
Covering the fruit by slipping a paper bag over each cluster soon after the berries are formed, and letting remain till ripe, is found a complete protection from rot, and also from insects and birds. The bags are those in common use by grocers, the size six by nine inches, and costing about $2.00 per 1000. They are fastened around the stem of the clusters with two pins - of course allowing space for the fruit to grow. One gentleman near Cincinnati saves from 5000 to 7000 clusters per year in this way, largely of Catawbas, and finds the quality very superior. The cost, including labor, he estimates at only one-third of a cent per cluster. This method is likely to be quite extensively used by amateur growers, if not for market.
Seeding the vineyard with oats in the Spring, so that the ground will be well covered with the crop at midsummer, then mowing and leaving it as a mulch on the surface till danger of rot is past, has been practiced by some of our grape growers with good results, especially on rich soils. It is a question whether the covering of herbage operates beneficially simply as a mulch protecting the vine root from the direct heat of the sun and the foliage from reflected heat, or whether the benefit results from the roots of the oat plants drawing off surplus moisture from the soil.' Experiments will be made the coming season to determine whether mulching with litter or sawdust has the same effect as oats. In one instance seeding the ground with clover and letting it lie without tillage for two seasons was of benefit in preventing rot, but caused serious check to the growth of the vines. In another case a crop of tomatoes growing between rows of grapes, so as to cover the soil, seemed to prevent the rotting of the fruit, as on a portion of the rows where the ground was naked the grapes rotted badly.
Training the vines on flat trellis or poles within a foot or two of the ground, and so as to cover or shade the entire surface, is also said to have secured exemption from rot; and in one case this result was gained by training vines on poles directly over a small stream of running water.
Fertilizing the roots of vines with ashes, bone dust and superphosphate, where the soil is rather poor, has been found beneficial in promoting the growth of vines but not in lessening the tendency to rot. Under-draining the soil is also found of no advantage in this respect, as it tends to favor the admission of water from Summer rains and to retain it about the roots, when the aim should be to have it run off the surface as quickly as possible. The best seasons for our grape crop are those having the least rain fall during June and July.
Some persons have suspected insect agency of being the cause of the rot, as in many cases the diseased berries have a mark like the puncture of an insect, but these marks are not general, and the closest observers have been unable to find any insect at such work when the disease makes its appearance. The bag remedy is referred to as favoring the insect theory, but other remedies conflict with it, and the bag remedy does not conflict with the idea that the cause of the disease is atmospheric.
It is difficult to adopt a theory on this subject that will harmonize with all the facts observed, and our aim at present is to induce more persons to observe facts and try experiments. When more of this work has been carefully done will be time to theorize.
Mr. Wm. Saunders, superintendent of the public gardens at Washington, recommended the covered trellis as a protection from mildew (perinospora), in the Report of the Department of Agriculture for 1861. In a letter written by him last November, and read by me at our annual meeting, after speaking of the want of more systematic observation respecting grape rot, he says:
"It seems to me that a special commission of practical men should be appointed to visit vineyards during the Summer of 1879, with a view to more explicit observations on grape rot than we now possess. Isolated observations by different parties in different climates, and under different conditions of soils and locations will always prove unsatisfactory. Many apparent contradictions can be reconciled by simultaneous and systematic observations, and the interest of grape culture would seem to fully justify State appropriations for this purpose. Well directed efforts in this line could not fail of adding to our direct knowledge of this disease of the grape".