BLIGHT. 



BLIGHT. 



BLIGHT. The general name for various 

 injuries received by, and diseases incident to, 

 com, fruit-trees, plants, &c. The terms blight 

 /ind blast, are indiscriminately applied to plants 

 injured by fungi, insects, disease, frost, &c. 

 Blight originating in cold, which, congealing the 

 sap of the tender shoots and leaves of plants, 

 causes these to perish from the bursting of their 

 sap-vessels. Blight sometimes results from 

 causes the very opposite of this, namely during 

 the prevalence of very sultry, or very dry winds, 

 the effects of which are popularly termed fire- 

 blights, and are similar to those which some- 

 times injure the vineyards of Italy, and the hop- 

 grounds of England. What is called in England 

 the white blight is supposed to originate from 

 want of nourishment. It is most commonly met 

 with in grain fields during very dry spells of 

 weather, especially on thin gravelly soils, 

 when the plants get into head or blossom pre- 

 maturely, and the head or seed-pod ripens 

 without filling. 



The mildew, one of the greatest enemies that 

 the agriculturist has to contend with, is nothing 

 more than several species of parasitical fungi, 

 or very minute plants of the mushroom species, 

 which attack different kinds of plants, grain, &c. 

 It varies in its nature and appearance, accord- 

 ing to the plants attacked. (See Pl.2,/,ra,H,&c.) 



Blight originating in fungi, attacks the leaves 

 or stems both of herbaceous and woody plants, 

 such as the common barberry and buckthorn, 

 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 pre- 

 ceeded by cold, moist weather, which happen- 

 ing in the warm month of July, suddenly 

 chills and checks vegetation. It generally as- 

 sumes the appearance of a rusty-looking 

 powder that soils the finger when touched. In 

 March, 1807, some blades of wheat attacked 

 by this species of blight were examined by 

 Keith ; the appearance was that of a number 

 of rusty-looking 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 inspec- 

 tion, these patches were found to consist of 

 thousands of small globules collected mto 

 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.} This fungus has been 

 figured by Sowerby and by F. Bauer and Grew. 

 I is known among farmers by the name of red 

 rust, arid chiefly affects the stalks and leaves. 

 But there is another species of fungus known to 

 the European fanner 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 

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I transparent fibres. The globules are filled 

 with a fine powder, which explodes when they 

 are put into water. It is very generally accom- 

 j panied with a maggot of a yellow colour, which 

 I preys also upon the grain, and increases the 

 amount of injury. 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 naanured earths in which 

 the plant grows, it will be unable to perfect its 

 fruit, which of consequence becomes more 

 liable to disease. (New Theory of Agr.) 



Smut is a disease incidental to cultivated 

 corn, 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 drop of water and put 

 under the microscope, it will be found to con- 

 sist of millions of minute and transparent 

 globules, which seem to be composed of a clear 

 and glairy fluid encompassed by a thin and 

 skinny membrane. This disease does not 

 affect the whole body of the crop, but tha 

 smutted ears are sometimes very numerously 

 dispersed throughout it. Some have attributed 

 it to the soil in which the grain is sown, and 

 others have attributed it to the seed itself, alleg- 

 ing that smutted seed will produce a smutted 

 crop; .but in all this there seems to be a great 

 deal of doubt. Wildenow regards it as originat- 

 ing in a small fungus, which multiplies and 

 extends till it occupies the whole ear (Princip. 

 of Bot. p. 356) j but F. Bauer, of Kew, seems 

 to have ascertained it to be merely a morbid 

 swelling of the ear, and not at all connected 

 with the growth of a fungus. (Smith's Introd 

 p. 282.) It is said to be prevented by steeping 

 the grain, before sowing, in a weak solution 

 of arsenic. But, besides the disease called 

 smut, there is also a disease analogous to it, 

 or a different stage of the same disease, known 

 to the farmer by the names of bags or smut 

 balls, in which the nucleus of the seed only 

 is converted into a black powder, whilst the 

 ovary, as well, as the husk, remains sound. 

 The ear is not much altered in its external ap- 

 pearance, and the diseased grain contained in 

 it will even bear the operation of thrashing, 

 and consequently mingle with the bulk; but 

 j it is always readily detected by the experienced 

 j buyer, and fatal to the character of the sample. 

 It is said to be prevented as in the case of 

 smut. This disorder, so very fatal to the cha- 

 racter of wheat from the injury it does to flour, 

 ', is known in some of the United States by the 

 very homely name of bn*t. 



Mildew is a thin and whitish coating with 

 which the leaves of vegetables are sometimes 

 covered, occasioning their decay and death, 

 and injuring the health of the plant. It is fre- 

 quently found on the leaves of hops, hazlenut, 

 and the white and yellow dead-nettle. It is 



