Blights are generally supposed to be produced by easterly winds, which convey multitudes of the eggs of insects from some distant quarter; and these being lodged on the surface of the leaves and flowers of fruit-trees, cause them to shrivel and decay.
It is the general opinion, that one principal reason why the entitans of London are particularly subject to blights, is the great number of pruned trees and cut hedges near the metropolis; for as all vegetables become more or less sickly when the course of their sap is impeded, the trees in this state are more liable to blight, than such as are vigorous and uninjured by the pruning-knife. It is worthy of remark, that to the westward of London the effects of this distemper insensibly decrease, insomuch, that at forty miles distance it rarely occurs, and at an hundred miles and upwards, it is entirely unknown. This circumstance seems to favour the idea of its being con-veyed by easterly winds. But the true cause appears to be, the continuance of these winds for several days, without the intervention of showers or dews, by which the expansion of the tender blossom is checked, so that the young leaves necessarily wither.
To cure this distemper, some persons burn a quantity of wet litter on the windward side of the plants, as it is supposed that the smoke will suffocate the insects : others fumigate the trees, by strewing sulphur upon lighted charcoal, or by sprinkling them with to-bacco-dust, or with water in Which tobacco-stalks have been infused for twelve hours. Ground-pepper, scattered over the blossoms, has sometimes proved beneficial.
Mr. Gullett, of Tavistock, is of opinion that great benefit may be derived from whipping the branches of fruit-trees with a bunch of elder-twigs, the leaves of which should be previously bruised. The smell of the elder being extremely disagreeable, no insects will settle on the parts touched by it ; and some blighted shoots have even been restored, by first whipping them, and then tying up a bunch of elder-leaves among them.
But the most effectual remedy is, to wash the plants gently and frequently with pure water, and if the young shoots be much infected, to rub them gently with a woollen cloth, in order to clear away the glutinous matter. This operation should be performed in the morning, that the moisture may be exhaled before night.
Blight. - This being one of the most destructive, distempers to fruit-trees, we shall give an account of the different remedies that have been proposed by Mr. Forsyth, both for its prevention and cure, according to the various causes from which it may originate.
Where the blight arises from long-continued easterly winds, the diseased tree ought to be washed with a mixture of urine and soapsuds : this operation must be performed as early as possible; for the malady may thus be in a great measure prevented; but, if the young and tender shoots be greatly infected, it will be advisable to cleanse them with a woollen cloth, dipped in the following liquor: Take 1lb. of tobacco, 2 lbs. of sulphur, 1 peck of unslacked lime, and about llb. of elder-buds ; let 10 gallons of boiling water be poured on these ingredients into a hogshead, which must now be closely covered, and the whole be suffered to become cool. The vessel is then to be filled up with cold water; and, after standing two or three days, during which time the liquor must be skimmed, the mixture will be fit for use.
Another cause of blight in the spring, is the sharp hoar frost, which often takes place during the night, and is succeeded by hot days ; so that the blossoms and fruit inevitably perish. The only preventive of such accidents, hitherto known, is the covering of walls with old fish-nets, doubled three times; and, if a few branches of dry fern be placed between the boughs, they will greatly contribute to break the force of high winds, as well as of the frost. Such shelter ought to be employed only during the night, and be removed in the day time. Thus, the fruit will be effectually preserved ; and, as the apparent trouble attending this practice might deter many persons from adopting it, Mr. F. is of opinion, that the object may be easily and expeditiously attained, by contriving to draw up and let down the nets by means of pullies.
Frequently, however, the affection termed blight, is merely a weakness in the trees, which de-pends on the difference of their constitutions, and proceeds from want of Draper nourishment; some bad quality in the soil; or from a distemper in the stock, buds, or scyons; all of which causes produce a malady in trees, that is with difficulty cured.
Should the cause arise from the soil, Mr. F. directs it to be dug out, and supplied with fresh mould, or, it will be advisable to remove the trees, and to plant others, which are better adapted to the ground ; because it is indispensably necessary to suit different kinds of fruit-trees, as nearly as possible, to the nature of the land. But, where the weakness of trees is induced by some inbred disease, they ought to be dug up ; the earth be changed ; and other plants be sub-stituted.
Lastly, there is another species of blight, that is very destructive to orchards and plantations, in the months of April and May: it is known under the name of Blast. This malady is conjectured to originate from certain transparent floating vapours, which assume such forms as to converge the rays of the sun, in a manner similar to a burning glass, and to scorch those plants on which they happen to descend, in a greater or less degree, according to their convergen-cy. The blast occurs most frequently in close plantations, where the exhalation of vapours from the earth, and the perspiration of the trees are confined, for want of a sufficient circulation of the air to disperse them. Mr. F'oRsyth, therefore, recommends a clear, healthy spot, to be selected for kitchen - gardens, orchards, etc. ; the trees being planted at such a distance as to give free admission to the air; so that all noxious vapours may be dissipated, before they are formed into volumes capable of occasioning blasts.