260 SCIENCE OF AGRICULTURE. Part II. 



1 686. Blight. Much has been written on the nature of blight ; and in proportion as 

 words have been multiplied on the subject, the difficulties attending its elucidation have 

 increased. 



1687. The blight, or blast, was well known to the ancient Greeks, who were, however, totally ignoram, 

 of its cause, regarding it merely as a blast from heaven, indicating the wrath of their offended deities, and 

 utterly incapable of prevention or cure. It was known also to the Romans under the denomination 

 of rub)go, who regarded it in the same light as the Greeks, and even believed it to be under the direction 

 of a particular deity, Rub'igus, whom they solemnly invoked that blight might be kept from corn and 

 trees. It is still well known from its effects to every one having the least knowledge of husbandry or gar- 

 dening ; but it has been very differently accounted for : and, perhaps, there is no one cause that will 

 account for all the different cases of blight, or disease going by the name of blight ; though they have 

 been supposed to have all the same origin. If we take the term in its most general acceptation, it will 

 include at least four distinct species, blight originating in cold and frosty winds ; blight originating in 

 a sort of sultry and pestilential vapour ; blight originating from want of nourishment ; and blight origi- 

 nating in the immoderate propagation of a sort of small and parasitical fungus. 



1688. Blight originating in cold and frosty winds, is often occasioned by the cold and easterly winds 

 of spring, which nip and destroy the tender shoots of the plant, by stopping the current of the juices. 

 The leaves which are thus deprived of their due nourishment wither and fall, and the juices which are 

 now stopped in their passage swell and burst the vessels, and become the food of innumerable little insects 

 which soon after make their appearance. Hence they are often mistaken for the cause of the disease 

 itself; the farmer supposing they are wafted to him on the east wind, while they are only generated in 

 the extravasated juices as forming a proper nidus for their eggs. Their multiplication will no doubt con- 

 tribute to the spread of the disorder, as they always breed fast where they find plenty of food. But a 

 similar disease is often occasioned by the early frost of spring. If the weather is prematurely mild, the 

 blossom is prematurely protruded, which, though it is viewed by the unexperienced with delight, yet it is 

 viewed by the judicious with fear. For it very often happens that this premature blossom is totally de- 

 stroyed by subsequent frosts, as well as both the leaves and shoots, which consequently wither and fall, 

 and injure if they do not actually kill the plant. This evil is also often augmented by the unskilful 

 gardener, even in attempting to prevent it ; that is, by matting up his trees too closely, or by keeping 

 them covered in the course of the day, and thus rendering the shoots so tender that they can scarcely 

 fail to be.destroyed by the next frost. 



1689. Blight, originating in sultry and pestilential vapour, generally happens in the summer, when the 

 grain has attained to its full growth, and when there are no cold winds or frosts to occasion it. Such was 

 the blight that used to damage the vineyards of ancient Italy, and which is yet found to damage our hop- 

 plantations and wheat-crops. Tlie Romans observed that it generally happened after short but heavy 

 showers occurring about noon, and followed by clear sunshine, about the season of the ripening of the 

 grapes, and that the middle of the vineyard suffered the most. This corresponds pretty nearly to what 

 is in this country called the fire-blast among hops, which has been observed to take place most com- 

 monly about the end of July, when there has been rain with a hot gleam of sunshine immediately after; 

 the middle of the hop-ground is also the most affected, whether the blight is general or partial, and i^ 

 almost always the point in which it originates. In a particular case which was minutely observed, the 

 damage happened a little before noon, and the blight ran in a line forming a right angle with the sun- 

 beams at that time of the day. There was but little wind, which was, however, in the line of the blight. 

 (Hale's Body of Husbandry.) Wheat is also affected with a similar sort of blight, and about the same 

 season of the year, which totally destroys the crop. In the summer of 1809, a field of wheat, on rather a 

 light and sandy soil, came up with every appearance of health, and also into ear with a fair prospect of 

 ripening well. About the beginning of July it was considered as exceeding any thing expected from such 

 a soil. A week afterwards a portion of the crop on the east side of the field, to the extent of several acres, 

 was totally destroyed ; being shrunk and shrivelled up to less than one half the size of what it had for- 

 merly been, and so withered and blasted as not to appear to belong to the same field. The rest of the 

 field produced a fair crop. 



1690. Blight from want of nourishment may happen to all plants, wild or cultivated ; but it is most 

 commonly met with in corn fields, in very dry seasons, in those thin gravelly surfaces which do not 

 sufficiently retain the moisture. In such spots the plants are thrown prematurely into blossom, and the 

 ear or seed-pod ripens before it is filled. In England the farmers call this the white blight 



1691. Blight, originating in YUngi, attacks the leaves or stems both of herbaceous and woody plants, 

 such as uph6rb/a Cypanssias, ^erberis vulgaris, and iihamnus catharticus ; but more generally grasses, 

 and particularly our most useful grains, wheat, barley, and oats. It always appears in the least ventilated 

 parts of a field, and has generally been preceded by cold, moist weather, which, happening in the warm 

 month of July, suddenly chills and checks vegetation. It generally assumes the appearance of a rusty- 

 looking powder, that soils the finger when touched. In March, 1807, some blades of wheat attacked with 

 this species of blight were examined by Keith ; the appearance was that of a number of rusty-look- 

 ing spots or patches dispersed over the surface of the leaf, exactly like that of the seeds of dorsiferous 

 ferns bursting their indusium. Upon more minute inspection, these patches were found to consist of 

 thousands of small globules collected into groups beneath the epidermis, which they raised up in a sort of 

 blister, and at last burst. Some of the globules seemed as if embedded even in the longitudinal vessels of 

 the blade. They were of a yellowish or rusty brown, and somewhat transparent. But these groups of 

 globules have been ascertained by Sir J. Banks to be patches of a minute fungus, the seeds of which, as 

 they float in the air, enter the pores of the epidermis of the leaf, particularly if the plant is sickly ; or 

 they exist in the manure or soil, and enter by the pores of the root {Sir J. Banks on Blight, 1805.) 

 This fungus has been figured by Sowerby, and by F. Bauer and Grew. It is known among farmers by 

 the name of red rust, and chiefly affects the stalks and leaves. But there is another species of fungus 

 known to the farmer by the name of red gum, which attacks the ear only, and is extremely prejudicial. 

 In the aggregate it consists of groups of minute globules interspersed with transparent fibres. The glo- 

 bules are filled with a fine powdery which explodes when they are put into water. It is very generally 

 accompanied with a maggot of a yellow colour, which preys also upon the grain, and increases the amount 

 of injury. 



1692. The only means of preventing or lessening the effect of any of the different varieties of blight 

 mentioned is proper culture. Palliatives are to be found in topical applications, such as flower of sul- 

 phur, and where the disease proceeds from, or consists of, innumerable minute insects, it may occasionally 

 be removed. Grisenthwaite conjectures that in many cases in which the blight and mildew attack corn- 

 crops, it may be for want of the peculiar food requisite for perfecting the grain ; it being known that the 

 fruit or seeds of many plants contain primitive principles not found in the rest of the plant Thus the 

 grain of wheat contains gluten and phosphate of lime, and where these are wanting in the soil, that is, 

 in the manured earths in which the plant grows, it will be unable to perfect its fruit, which of conse;. 

 quence becomes more liable to disease. {Hevu Theory of Agr.) 



1693. Smut is a disease incidental to cultivated com, by which the farina of the grain, 

 together with its proper integuments and even part of the husk, is converted into a black 

 soot-like powder. If the injured ear be struck with the finger, the powder will be 

 dispersed like a cloud of black smoke ; and if a portion of the powder be wetted by a 



