70 FIFTH ANNUAL REPORT 



flown ; and there is no longer any doubt — as there had never existed 

 any in the minds of entomologists — about their flying capacity. On 

 a calm, clear day, the latter part of last June, it was my fortune to 

 witness a closely allied species {Phylloxera carymfolim) of the same 

 size and proportions, swarming on the wing to such an extent that to 

 look against the sun revealed them as a myriad silver specula. They 

 settled on my clothing by dozens, and any substance in the vicinity 



tut either because my answer did not reach him in time, or because it explained away his antecedent 

 objections, and would necessitate their expuuging, my answer to said letter does not appear. 



It is an uuproiitable business to have to meet theories and objections which have in tliemselves 

 little force; but, lest silence should be construed into acquiescence in M. Laliman's views, I have 

 deemed these few remarks proper, though somewhat irrelevant and of import to but few. While thus 

 reprehending M. Laliman, I heartily concur iu his advice to import from America vines which have 

 best resisted the PhyUoxera, and in the caution urged upon those who would import all the Labyuscas. 



PTtOOF OF THE OCCURRENCE IX AJIERICA OF OIDIUM TUCKERI, OF EUROPE. 



Communicated by Mr. Wm. Saunders, of the Department of Agriculture. 



It is now twenty years since I became convinced of the presence of Oidium Tuckeri in this country . 

 Previous to that time I had been giving what .attention I could to the study of mildew — its origin, 

 causes, etc. I early became convinced that there were two very distinct forms appearing on the 

 grape-vine, and moreover, that one of tliese forms was most prevalent in dry weather, and the other 

 in damp weather. It had been ascertained that the foreign grape, even when grown under glass in 

 this climate, was very liable to attacks of mildew; and in all book directions, at that time, as to its 

 culture, sulphur applications were constantly recommended. From its close resemblance to the pea 

 Erysiphc of Europe, that I had often seen iu England, attacking peas in dry summers, (aud only dur- 

 ing periods of great drouth,) I conchuled this mildew, appearing like a white down, or floury mass, on 

 the upper surface of the leaves of grapes in the glass grapery, and occasionally spreading itself over 

 the young green shoots and berries, was an Erysiphe ; L named this in my hrst published notices (see 

 Phit. Florist, 1802, and Horticulturist, ISoo,) as an Erysiphe. I reached this conclusion from other 

 points— notably, the English gooseberry, Persian Lilacs, English hawthorns, oaks, etc. These, when 

 grown in this warm and arid climate, become covered with this same, or a very closely allied form of 

 Erysiphe. Belore promulgating this opinion, I had, as has always been and still is my practice, to 

 lirst verify to my own satisfaction the truth of my statements. Acting upon the theory that this form 

 of mildew was produced on the foreign grape in graperies, as well as oftentimes in the open air, by 

 dryness, I commenced and have since recommended a mode of ti-eatment, which is now generally 

 followed, and which entirely obviates any necessity for sulphur applications, because it prevents the 

 occurrence of the conditions necessary for the growth of this fungus. The treatment is, briefly, to 

 ventilate graperies only from the top of the house, never opening any side sashes that will allow a cur- 

 rent of dry air to come from the exterior and circulate out at top, carrying with it the moisture of the 

 house; also to maintain a moist atmosphere by keeping the floor of the house constantly damp, and 

 sprinkling water freely on very bright days, so" that as the temperature increases the atmospheric mois- 

 ture will also be proportionately increased. Vv^hen this practice is fairly carried out, no mildew of an 

 Erysiphe kind will make its appearance. I did not then, so far as I now cau recollect, connect this 

 mildew with the Oidium of Europe, until later, when it was discovered that the so-called Oidium 

 I'uckeri -was shnply a iorm oi Erysijihe, or rather a transformation occurring during its growth. (I 

 think that this Oidium or Erysiphc has not yet fruited in England.) This led me to further investiga- 

 tions, and proved to me that our Erysiphe was really and truly the Oidium Tuckeri of England, and 

 moreover, that the plant perfected itself fully iu this climate. This was my conviction lifteen years 

 ago; recent microscopical investigations prove beyond doubt the correctness of my suppositions. 



But we very rarely observe this Erysiphe on our native grapes in ordinary vineyard culture, 

 although it is frequently to be found on vines growing in warm, very sunny, sheltered, dry positions, 

 such as may always be found in city yards. It is not by any means conlined to these, however. Last 

 summer we hail plenty of it on the leaves of many varieties growing on our trellis here. As already 

 remarked, this mildew shows a powdery appearance on the upper surface of leaves, and frequently 

 forms a somewhat leathery coating on shoots and berries. Its eUects are to corrode and prevent the 

 further swelling of the parts attacked. Grapes, for mstance, that are touched by it, will show an in- 

 durated spot, hard and brown, the portions of the berry not attacked will swell out freely, and all 

 that this hurt portion cau do is to crack open, ^^hich it usually does, and the seeds may freciuently be 

 seen to protrude from this crack. 



But the mildew most injurious to our native grapes is altogether different. This is a Peronospora, 

 and shows itselt on the under surface of the leaves, usually looking like a small patch of whitish- 

 browu downy matter. It adheres closely to the leaf, and is a perfect parasite; it tiestroys the part 

 Where it adheres, the sun burns a hole, and it is called blister, leaf-blight, etc. But it you say that it 

 is mildew— oh, no ! I never had any mildew. I have lots of amusing incidents of this kind iu my mind. 

 Some whose vines were all but denuded of foliage would still insLst that Ihey never had a case of mil- 

 dew, until I convinced them of the facts, and pointed out the mildew to their wonilering eyes. Being 

 contined to the under surface of the leaves, it escapes observation. This mildew is encouraged by 

 dami)ness on the foliage, by continued damp, rainy weather, or even constant heavy dews, followed 

 by still, balmy days; anything in fact that will prevent moisture from quickly leaving the foliage. 



About 1857, I tried a board covering over a trellis of Catawbas that yearly failed to mature their 

 fruit, owing to the destruction of the foliage during summer by this mildew, and the eflect was all that 

 could be desired. In the Agricultural Report for Isiil you will lind this aflair iigured. This covering 

 prevents the radiation of heat I'rom the plants, consequently they are not rendered so cold as to con- 

 dense upon them the moisture of the air and form dew. A series of observations made many years 

 ago with registering thermometers explained to me the modus operandi of the whole. IJuring still, 

 clear nights in July, I lound that the thermometer, having clear two feet from the trellis, would fall 

 from five to ten degrees lower than the thermometer dire(!tly under the cover. 



