544 EXPEBIMENT STATION EECOED. 



than upon atmospheric conditions, which are largely influential in the case 

 of mildew. 



The black rot organism is very resistant to both acids and alkalis. 



Studies on grape mildew, L. Ravaz and G. Vekge (Prog. Agr. et Tit. (Ed. 

 VEst-Ccntre), 32 {1915), Xos. 22, pp. 513-522, figs. 15: 23, pp. 537-5U, fig- 1 ; 

 25. pp. 584-590, figs. 5). — Detailing the results of studies carried on for several 

 years with grape downy mildew {Plasmopara viticola), the authors state that 

 the first contamination is due to macroconidia issuing from winter spores scat- 

 tered on the ground. This may be cousidere<l as a first invasion, which may 

 occur without the organism reaching the vine. If the zoospores produced by 

 the macroconidia find vegetation sufficiently advanced, they cause the first 

 contamination, whence issues the second invasion, which may be the first of the 

 vine. If the latter is not far advanced, as in case of late varieties, the zoo- 

 spores die without producing the disease. 



To be effective, a copper solution should cover all portions liable to attack. 

 In 1915 the appearance of the conidia was announced five or six »lays previous 

 to the appearance of the oil spots, giving sufficient time for spraying. 



The necessity is pointed out for the piompt recognition and announcement of 

 conditions favoring an outbreak, also the appearance of infecting material and 

 the time for employment of protective measures. 



Sprays rich in soluble copper. K. Rabat£ (Rev. Vit., 42 (1915), No. 1088, 

 pp. 377-381). — Discussing some results of recent study, the author states that 

 an effective spray for downy mildew is made by adding to a Bordeaux mix- 

 ture containing 2 per cent of copper sulphate, 0.25 per cent of copper sulphate 

 just before use, 0.25 per cent aminonia, and 0.00 to 0.08 per cent casein «liluted 

 in water with as much lime in the form of powder or paste, or 1 per cent 

 molasses in water. 



Oidium or powdery mildew of the vine, F. T. Bioletti and F. C. H. Floss- 

 I'EDER (California Sta. Circ. 144 (1915), pp. 12, figs. 7). — According to the 

 authors, Oldlum is a serious disease of grapes in California, being found in 

 every vineyard section. In sonie regions, particularly in tlie cooler, nioister 

 districts, great damage is frequently caused, while in hotter, drier district.s, 

 little damage is observed except on the more susceptible varieties. 



Experiments are reported in which an attempt was niatle to control the powdery 

 mildew by sulpliuring the vines with a good commercial brand of sulphur ap- 

 plied with knapsack bellows, a liquid spray of .sulphur mixed with inert matter 

 so as to cause ready mixture with water, and a winter treatment in wliich 

 vines were sprayed with a copper sulphate solution. The application of dry 

 .sulphur was found most efficient in treating the vines. Winter treatments 

 appeared to be unnecessary and useless. The cost of perfect control with four 

 dry sulphurings was 70 cts. per acre. Directions are given for selecting a good 

 quality of sulphur and for its application. 



Treatment for chlorosis, .T. IvARMeili,£re (Rev. Vit., 42 (1915). Xn. 1084, PP- 

 293-295). — A brief discussion is given regarding the effects of «lifferent limy 

 soils in producing chlorosis in grapevines, also of the iron sulphate treatment for 

 the stocks. 



Partial pruning and immediate painting of the cut .surfaces with an iron 

 sulphate solution of 30 per cent strength (or even 40 per cent in case of older 

 wood) is deemed efficacious if timely, that is, if done while the sap pressure is 

 negative so as to insure ready entrance of the solution. This is said to afford 

 also a degree of protection against the effects of early frost. The treatment is 

 less effective if given soon after a rain. A liberal allowance of iron sulphate 

 spread upon the snow is said to be taken up by the roots with good result.s and 

 the addition of sulphuric acid has been found lieneficial. 



