340 THE YEAR-BOOK OF AGRICULTURE. 



The Oidium Tuckeri, or Grape Malady of Europe, 



FROM a paper read before the Royal Institution of Great Britain, by M. Brockedon, we ob- 

 tain the following information respecting the singular disease which has of late years proved 

 so destructive to grapes of France and other parts of Europe : 



It appears to have been first observed in England by an observant gardener of Margate, 

 whose name has been given to the fungus producing the disease viz. Oidiunfc Tuckeri. It is 

 an egg-shaped fungus, one of an immense family of this class of destroyers, but one not be- 

 fore known or recognised ; and though it bears a close resemblance to those which are found 

 upon the potatoe, peach, cucumber, &c., yet it is distinguished from all others by a micro- 

 scopic observer, and has never yet been found upon any other plant, and, when found upon 

 the grape, has always been destructive. Its first appearance is like a whitish mildew, showing 

 itself principally upon the young grape when about the size of a pea. When the spore of 

 this fungus has settled on the young berry, it enlarges and radiates irregularly in fine fila- 

 ments, which often cover the whole surface, extending with great rapidity. These fix them- 

 selves by imperceptible attachments, which do not appear to penetrate the cuticle ; numerous 

 branches from the mycelium are unfruitful ; others are jointed, and rise vertically like the 

 pile of velvet ; the upper joint enlarges, rounds itself into an elliptical form, ripens, separates, 

 and is carried off with the slightest motion of the air, to find another grape upon which it can 

 be developed. Warmth and moisture favor its rapid fructification ; a succession of spores 

 rise from the same branch, and often two, three, or four ripen and disperse almost at the 

 same time. Its effect upon the grape is to exhaust the juices of the cuticle, which ceases to 

 expand with the pulp of the fruit ; it then bursts, dries up, and is utterly destroyed. This 

 fatal disease has returned with increased virulence in each succeeding year. In 1847 the 

 spores of this Oidium reached France, and was found in the forcing-houses of Versailles and 

 other places near Paris ; but the disease soon reached the trellised vines, and destroyed the 

 grapes out of doors in the neighborhood, and continued to extend from place to place ; but 

 until 1850 it was chiefly observed in vineries, which lost from this cause, season after season, 

 the whole of their crops. Unhappily, in 1851, it was found to have extended to the south and 

 south-east of France and Italy, and the grapes were so affected that they either decayed, or 

 the wine made from them was detestable. In 1852, the Oidium Tuckeri reappeared in France 

 with increased and fatal energy ; it crossed the Mediterranean to Algeria, has shown itself in 

 Syria and Asia Minor, attacked the Muscat grapes at Malaga, injured the vines in the Balearic 

 Islands, utterly destroyed the vintage in Madeira, greatly injured it in the Greek Islands, and 

 destroyed the currants in Zante and Cephalonia, rendering them almost unfit for use ; and so 

 diminished the supply, that five hundred gatherers did the ordinary work of eight thousand ! 

 But it is in France that its frightful ravages are chiefly to be regarded as a national calamity, 

 where the produce of the soil in wine is said to exceed five hundred millions of hectolitres ; 

 two-fifths of the usual quantity of wine made there has been destroyed, and what has been 

 made is bad. It has not touched with equal severity all the departments. 



M. Mdhl has most carefully examined whether the Oidium of the grape lives on other plants 

 besides the vine, but he is decidedly of opinion that it does not. Some persons have supposed 

 that it was caused by insects, because occasionally they have been found on diseased vines ; 

 but the idea is now utterly rejected, for not the slightest appearance of disease precedes the 

 fungus, which creeps over the epidermis, but does not enter its tissues. It envelops the grape, 

 absorbs the juices of the superficial cells, and stops the growth of the cuticle. The pulp 

 expands within the fruit, bursts longitudinally, its juices are lost, and it dries up. In an 

 early stage of the disease the fungus may be wiped off, and the fruit will come to maturity. 

 The Oidium never matures on decayed vegetable substances ; it lives and fructifies only on 

 living tissues. By many it is asked, Is the Oidium the cause, or the consequence of the dis- 

 ease of the vine. The vine, one party says, is over-cultivated and liable to affections which 

 the wild healthy plant resists, and it should be treated as in a state of plethora : tap it, lessen 

 its sap, and it will invigorate so as to resist the poison of the Oidium. This has been tried 

 and has failed. If this were the cause, also, it could not have so suddenly and widely ex- 

 tended itself. 



