Mildew. 



GRAPE MANUAL. 



Peronospora. 



VITICULTURAL REMARKS. 



The American* MILDEW (Peronospora viticola) first 

 presents itself in the form of spots resembling a small 

 accumulation of powdered sugar, not larger than a 

 lentil, on the underside of the leaf; but imperceptibly 

 these spots extend and join until they cover a larger 

 portion of the entire lower face of the foliage. Later 

 still, the centers of attack dry up and take the color of 

 brown or dead leaves, so that these mildewed, shriv- 

 elled, dried-up leaves are often confounded with or 

 taken for "sun-scald"; but on closer observation mil- 

 dew can easily be distinguished from sun-scald. If 

 the effect of the latter, there is no white powdery 

 mushroom vegetation visible on the lower face of the 

 leaf. Mildew mostly attacks the foliage, sometimes 

 also the young green stems ; rarely the small, young, 

 never the full-grown, ripening berries. 



The important difference between Perenospora (the 

 Am. mildew) and Oidium (the European mildew) is 

 not only that Perenospora appears on the lower, while 

 Oidium appears on the upper surface, but that the 

 former penetrates the entire tissue of the leaf, while 

 Oidium grows on its upper surface only. Humidity 

 and dryness exert a preponderating influence on the 

 development of the disease; rain, dew, even fog, favor 

 the spread and germination of the spores, while a pro- 

 longed drouth restricts and kills them. 



As a Remedy sulphurizing was long and strenuously 

 recommended. In France and Germany mildew is 

 successfully combatted with sulphur, early and often 

 applied; why should it not be the remedy here?(!) 

 Many articles were published in all our horticultural 

 magazines representing flour of sulphur as an infalli- 

 ble cure of mildew, prescribing quantity, time, and 

 mode of using it. Bellows were specially manufactured 

 for this purpose. Wine-growers were found to testify 

 to the efficacy of this panacea ; none contradicted ;f 

 so that we ourselves, failing to see its good effect after 

 repeated trials, merely ventured to say in the former 



* To distinguish this from the O'idium (the European 

 mildew) we call the Peronospora -'American mildew"; 

 but this dangerous fungus is by no means unknown in 

 Europe; and we doubt that it has come there from 

 this country, though it showed itself here much soon- 

 er. In Italy and also in Africa it has appeared in 

 many places where no American vine had ever 

 been grown, and it has been discovered even on wild 

 European vines. Rudolph Goethe, Director of the 

 Royal Horticult. Inst. at Geisenheim, on the Rhine, calls 

 it "false mildew.'" Victor Palliat, editor " Vigne Amer.", 

 has shown that it was known in France, long ago, under 

 the name of " melin." 



t The first honest testimony about the results of sul- 

 phurizing, in this country, we found in the " Vineland 

 Weekly " of Nov. 24, 1877, in an excellent study of THE 

 GKAPE ROT, by col. A. W. Pearson, from which we clip 

 the following : 



" Many, if not all, of those here who have used sulphur 

 this year for the first time are much disappointed in the 

 result. They either report no benefit whatever, or else 

 positive injury. Those who were more zealous than 

 prudent, and used sulphur liberally undiluted, of course 

 burned up their foliage, doing harm instead of good; 

 those, on the other hand, who used the preventive mo- 

 derately, and, asjthey considered, thoroughly, will un- 

 derstand, if this description of the disease has enabled 

 them to appreciate it, that "thoroughly," under the 

 atmospheric conditions of this summer, would almost 

 require that a sentry should be posted by each vine, 

 ready to scatter another sprinkling of the mixture be- 

 tween showers. 



" As already stated, I sulphured mine thirteen times, 

 and saved about one-third of the crop. Possibly by going 

 over them twenty-six times I might have saved another 

 third." 



edition of this Catalogue, that "with our prices of labor 

 it would scarcely be practicable and it is best not to 

 plant largely of those varieties which are very liable to 

 this disease." 



Not until this mildew (Peronospora) had also been 

 observed and studied in France, where it was. first 

 noticed in 1878, and only within these last four years, 

 during which it has spread all over Europe and parts- 

 of Africa, has it been recognized and fully established 

 that sulphurizing is quite ineffective against Perono- 

 spora, owing to the fact that this parasite, unlike the 

 Oidium, lives not merely on the surface of the leaf, but 

 permeates its tissue. 



Nevertheless we are not without hope that some 

 remedy will be found. Eminent scientists will now 

 occupy themselves with this serious question, which 

 concerns European grape culture the more as their 

 varieties (Vinifera) are all more subject to this disease 

 than our Americans. We have now before us an "Es- 



SAI SUB LE MlLDIOU, PAR A. MlLLAKDET, ProfeSSCUr il 



la Faculte des Sciences a Bordeaux," Paris, 1882 ; he 

 suggests, as a remedy, a mixture of powdered sulphate 

 of iron, copperas (4 Ibs.), with plaster of Paris, gyp- 

 sum (20 Ibs.), which, according to reports, was applied 

 (compte-rendu du congrfes international phylloxerique 

 de Bordeaux), with marked success. Remedies of this 

 kind must be used very cautiously ; and until their 

 efficiency and proper mode of appliance are estab- 

 lished, our grape-growers will do best to select those 

 varieties which are generally less liable to this disease. 

 To aid in doing so, the following table,* based on many 

 years' experience, may be of service : 



TABLE OF AMERICAN VINES (PRINCIPAL VARIETIES) WITH 

 REGARD TO THEIR RESISTANCE TO MILDEW (PeronOS- 



pora) . 



I. CATEGORY : almost entirely exempt, even in unfa- 

 vorable seasons and localities. 



jEstivalis, Northern Division ; Cynthiana, Nor- 

 ton's Virginia. 



Labrusca, Northern Division : Concord, Hartford, 

 Ives, Perkins ; also, Champion, Cottage, North 

 Carolina, Rentz, Venango. 



Riparia and its crosses with Labr. : Elvira, Mis- 

 souri Riesling, Montefiore, Noah, Taylor. 

 II. CATEGORY : suffering somewhat, but not seriously, 

 in exceptionally unfavorable seasons and local- 

 ities. 



JEstivalis, Southern Division: Cunningham;. 

 Northern Division : Hermann, Neosho. 



Labrusca, Northern Division: Dracut Amber, 

 Lady, Martha, N. Muscadine, Telegraph, Ma- 

 son's Seedling. 



Riparia and in its crosses with Labr, : Black 

 Pearl, Blue Dyer (Franklin), Clinton. 



Sybr., Labr. and Vinifera. Goethe. 

 III. CATEGORY : suffering seriously in unfavorable 

 seasons, and not recommendable for localities 

 usually exposed to> mildew. 



Mstivalis, Southern Division ; Devereux, Herbe- 

 mont, Lenoir, Louisana, Rulander. 



JEstivalis crossed with Vinifera (?) Alvey. 



Labrusca, Southern Division: Catawba, Diana, 

 Isabella. 



" Quelques Observations sur le Mildew, par G. & 

 Meissner," at the (Jongres international de Bordeaux. 



