This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
A great deal is written and published in Europe regarding the disease of the vine and potato. We have been attracted to a letter from Mr. John Malam, an Englishman, addressed to the Portuguese, French, and Spanish ambassadors, in which he says that as coal tar is one of the constituents contained in coal, which latter is of vegetable origin, and having been received from the atmosphere and soil as food for plants ages ago, I conceive it to be a very natural food for vegetation at the present period. The antiseptic, carboniferous, and ammoniacal products, distilled from coal, appear to me to be far better calculated to conduce to a healthy growth of plants, than the putrescent, foetid, nauseous, undecomposed animal and vegetable matters in use at the present time, which latter favor the attacks of fungi and insects. Goal tar being practically destitute of nitrogen, promotes a supply of carbonic acid to the roots of plants, whilst the other product, gas water, is very valuable as a manure, especially for cereal crops, from the nitrogen supplied by it to vegetation. I have found by experience, coal tar, mixed with farm-yard and stable manure, very beneficial for oats, melons, cucumbers, etc, and when dug into the rows before planting potato sets, a prevention to the disease.
It is a singular fact that the antiseptic properties of volatile hydro-carbons of coal tar have, in numerous instances, not only prevented the ravages of the vine and potato diseases, freeing the former in vineries from red spider, but have also prevented the ravages of cholera.
A Mr. Dido lately pointed out the absence of the Oidium on vines, the wood of which has been smeared over with coal tar. M. Sandette proposes a simple and inexpensive preservative, which proved successful in some experiments made during two years in the neighborhood of Bordeaux. In order to prevent and arrest the development of the oidium, it is sufficient, three weeks after pruning the vine, to smear the stem and shoots with liquid tar, applied with a brush. This operation costs very little, and has proved very successful on all plants in which it has been performed, even although they were in the midst of infected vines.
The writer thus concludes: I believe all antiseptics to be beneficial in neutralizing the effects of an excess of ozone; the flowers of sulphur, on this principle, are useful in arresting the ravages of the oidium, owing to the antiseptic properties of the sulphurous acid given oft' by them in a vitiated atmosphere being converted into sulphuric acid by the ozone. Gas tar not only contains antiseptic properties, but is also calculated to supply the plant with proper food, thereby rendering it healthy enough to bear, without injury, any vitiated state of the atmosphere. As the fungi on the diseased parts of the vine might be prejudicial to them if put in the soil near the roots, I would recommend all the diseased parts, when removed, to be burned, and the ashes dug into the soil.
In conclusion, I consider it the duty of all vine cultivators to endeavor to get at the root of the matter, and ascertain what is the predisposing cause of the disease in the vine, as no external application can effectually afford a cure. I should again recommend, then, that antiseptic manures should be dug into the soil, such as wood ashes (which contain potash,) gas tar, also doghead charcoal, lime, etc.; and the use of all putrescent animal and vegetable manure be abandoned, in order to restore the vine to its original state of health and natural productiveness.
Mr. Victor Chatel states that if the second and third sets of shoots of a Vine are cut away, the disease is much mitigated or wholly removed; but that to stop Vines, which is necessarily followed by shoots of a second or third development, is to increase the disease. This appears to arise from the softness of the leaves of the second and third class of shoots.