MILDEW. 



MILDEW. 



Thiri-skinmic.1 Sicilian { Gluten, 2397 

 wheat afforded of - \ Starch, 7^25 



Miiill"s!X wheat, ave-j Gluten, 190) 

 rae crop - - - \ Siurch, 765 j 



Spring wheat, 



C Gluten, 240 | 

 Starch, 700 f 



Miidewed wheat of 1804 



961 



940 

 650 



350 



Mildewed wheat of 1606J g'ljjjjjj' $ \ 210 790 



Showing, in one instance, a loss of 31 percent, 

 of flour in the mildewed when compared with 

 the average English wheat, and in the other of 

 nearly 74 per cent. (Elem. ofJlgr. Cheni. p. 150.) 

 Mr. W. Jones of Wilmington, Somerset, found 

 that wheat, partially mildewed, produced one- 

 fifth less of Hour than that not affected. 



I have almost always been able to detect the 

 Pitrri,iia upon the lower part of the culms, 

 generally on the shoot-blade (fnliir nt^nnnnx), 

 early in June; but it is not till the following 

 month that the season determines whether the 

 tfl of ibis funirus will be more than ordi- 

 narily extensive. Throughout July the English 

 farmer should scrupulously, and almost daily, 

 examine his wheat crop, especially that which 

 appears strongest and most luxuriant; and if 

 h- detects any considerable number of tufts of 

 the fungus upon the stems, must lose no time 

 in usinir those curative measures which will 

 be detailed in the close of this article. If July 

 is hot and dry, it maybe concluded, without 

 much fear of disappointment, that there will 

 be but little injury incurred by the mildew. 

 isoii of this is very apparent; for in 

 such a season no fungus will vegetate vigor- 

 ously. Th is order of plants invariably deli-hts 

 ami flourishes in a moist atmosphere, and in a 



1 li-ht, accompanied by gentle warmth. 



ISOB is the most expressive term to 



describe that wherein the mildew vegetates 



most rapidly. In such seasons likewise, it 



.iiately happens that the wheat plants 

 remain lori^'st .succulent, their pores expanded, 

 and their fibres relaxed; circumstances pecu- 

 liarly favourable to the admission of the seeds 

 of the fungus, to their vegetation, and to the 

 penetration of their roots. That it is in such 



- the Pttrnnia vegetates most rapidly and 

 extensively, is supported by the observations 

 of others ; for, although they consider such a 

 season as the actual cause of the mildew, their 

 testimony is equally valuable, though from it 

 they have drawn erroneous conclusions. Thus, 

 M. Duhamel says, that the mildew is caused by 

 mild, hazy, or gloomy weather, while the corn 

 is at the height of its vegetation ; that is, about 

 the time of its blooming. When a hot sun has 

 succeeded such weather, he observed the wheat 

 crops mildewed in a few days. He always 

 observed wet springs very productive of this 

 disease ; but it rarely occurs in clear, dry, hot 

 years. One or two writers have given most 

 incomprehensible theories of the cause of 

 mildew. 



Mr. R. Somerville concluded that the mildew 

 originates from the attacks of insects intro- 

 duced with the manure; but he evidently in- 

 tended by his descriptions the minute acarus 

 (a species of louse), which is almost always 

 to be found upon decaying vegetable matter; 

 and in the cases of mildews, this insect is the 

 follower, not the- introducer, of the disease. 



The Abbe Rozier,in his "Dictionary," observes 

 that it is "caused by the drops of fog or dew, 

 dissipated by a hot sun ;" an opinion which is 

 the echo of Ovid's verses forming part of the 

 Flamen's prayer for the preservation of the 

 Koman crops from this disease 



" Quantum, si cnltnos Titan incalfacit udos ; 

 Tune locus est irse Diva treinenda tuce." 



And such a season, as I have before observed, 

 has a damp atmosphere, which, above all other 

 states of the air, is favourable to the vegetation 

 of this Puccinia. There is no doubt, also, that 

 in such seasons vegetables are more than ordi- 

 narily weak and prone to disease, in which 

 condition they are likely to become the prey 

 of parasitic plants. "The application of cold 

 water to the plant," says Mr. Knight, "on which 

 the sun is shining strongly, is very injurious to 

 its health, and therefore likely to give increased 

 activity to any disease to which the plant is 

 subject." This observation follows the detail 

 of an experiment, in which he found that 

 sprinkling wheat plants growing on ground 

 very dry, with cold water, in the afternoon of a 

 warm, bright day, caused them to be exten- 

 sively mildewed. "A considerable absorption, 

 therefore, probably took place ; and to this ab- 

 sorption," says he, "and the effects of a sudden 

 change of temperature, as secondary causes, I 

 am disposed to attribute the appearance of the 

 disease ; but whether the seeds of the mildew 

 were carried into the pores of the plants by the 

 water, or existed there before, is a question 

 which I shall not attempt to solve." (/^/xA-.s, 

 On the might in Com, p. 30.) There is no dif- 

 ficulty in accounting whence the seeds of the 

 fungi came : for Mr. Knight records, in the 

 previous page, that other wheat plants close 

 by were extensively mildewed. 



The observations of Mr. Marshall, which 

 were the results of long experience in many 

 counties in England, coincide with the preced- 

 ing opinions. "In a dry, warm summer," he 

 remarks, "which is well known to be favoura- 

 ble to the health, vigour, and productiveness 

 of the wheat crop, the seeds of the fungi are 

 harmless, so long as the fine weather continues. 

 On the contrary, in a cold, wet season, which 

 gives languor and weakness to the wheat 

 plants, few crops escape entirely. A succes- 

 sion of cold rains, while the grain is forming, 

 is very inducive." Mr. Marshall previously 

 concludes that " The fungi are an effect, not 

 the cause of the disease ;" an error which is 

 at once refuted by the fact, that if all the fungi 

 are removed from a plant, it is speedily cured. 



Of other circumstances favourable or unfa- 

 vourable to the occurrence or exasperation of 

 mildew, little need be said, because they have 

 comparatively little influence upon its occur- 

 rence. All soils and situations are liable to 

 its incursions ; for it is, in the fullest sense of 

 the term, epidemic. The soil on which it ap- 

 pears the most rarely is a tenacious clay; and 

 that on which, when it does occur, its ravages 

 are the most extensive and destructive, is the 

 light, calcareous, and rich. " As far as my ob- 

 servations extend," says Mr. Egremont, " the 

 soils wherein clay predominates have yielded 

 crops the least affected by the mildew. The 

 soils most liable to have their crops injure.! 



811 



