1919] DISEASES OF PLANTS. 751 



Spraying [grapevines for dowiiy mildew] after July 15, A. Cadoret {Prog. 

 Agr. et Vitic. {Ed. VEst-Centre), 39 {1918), No. 27, pp. 9, iO).— Reaffirming 

 (E. S. R., 40, p. 750) the necessity and efficacy of thorougli spraying with 

 Bordeaux mixture at intervals of 8 to 12 days in very moist weather between 

 June 10 and July 15, or of monthly spraying during an ordinarily dry summer, 

 the author insists also on the necessity of prolonging such treatment until the 

 crop is gathered in case black rot is present. 



The action of copper on vegetation, A. Cadoret {Prog. Agr. et Vitic. {Ed. 

 VEst-Centre), 39 {1918), No. J,0, pp. 319, 3^0).— The author states from previous 

 observations, recorded above, that in ordinarily dry summers mildew attacks 

 during August are sufficient to decrease the foliage of grapevines. Vines 

 properly sprayed (as evidenced by the resulting blue coating) retain their 

 healthy appearance despite any deficiency of nutrition associated with lack of 

 moisture, therein showing resistance to drought as well as downy mildew. 

 The bearings of the facts observed are discussed. 



Further notes on the powdery mildews and the ammonium polysulphid 

 wash, J. V. Byre, E. S. Salmon, and L. K. Wormald {Jour. Bd. Ayr. [London], 

 25 {1919), No. 12, pp. 1494-1497).— Dnring the past three years further investi- 

 gations (E. S. R., 38, p. 853) have been carried out on the control of powdery 

 milde\^'S by means of washes containing sulphur. The object of the present 

 article is to give notice of new facts discovered relative to the killing point 

 of powdery mildews, and of an improved formula for making the concen- 

 trated ammonium polysulphid solution. The v;ork was carried out with hop 

 mildew {Sphwrotheca hmmili), but the facts as noted are thought to apply to 

 other mildews. 



In making up the stock solution, 1 gal. of a 30 per cent aqueous solution of 

 ammonia is saturated at ordinary temperature with hydrogen sulphid gas 

 until the density is 0.955. Two gallons of 30 per cent aqua ammoniac are 

 added and 112.5 oz. of sulphur stirred into the liquid. Hydrogen sulphid gas 

 is then passed through the liquid until all the sulphur dissolves and the density 

 reaches 1.036 at 17° C. (62.6° F.). The re.sulting clear dark-colored solution 

 constitutes the new stock solution, and this is referred to as ammonium poly- 

 sulphid stock solution, 1918, or as A. P. S., 1918. This should contain 19.2 per 

 cent ammonia and 24.2 per cent of sulphur, of which 10.6 per cent is in the 

 condition known as sulphid sulphur, and 13.6 per cent in the form known as 

 polysulphid sulphur. After standing 12 hours and being diluted with ap- 

 proximately 50 to 100 times as much water, the fluid may become cloudy and 

 finally thick with sulphur. 



To prepare this diluted wash 5 lbs. of soft soap (or 10 lbs. if the water is 

 very hard) are dissolved in 99 gal. of water, after which 1 gal. of the stock 

 solution, A. P. S., is added while stirring to give strength (a). Strength (b) 

 requires the same proportion of soap with twice the percentage of stock solu- 

 tion. Both these are to bo used as soon as made. Precautions as regards 

 handling are the same as those for lime sulphur. A nozzle giving a fine misty 

 spray is required. 



Lime-sulphur is thoroughly reliable for early sprayings against American 

 gooseberry mildew, but it should be dispensed with in favor of the above- 

 described wash before the marketing qualities of the berries are affected. 



Further data on the citrus canker affection of the citrus species and 

 varieties at Lamao, H. A. Lee {Philippine Agr. Rev., 11 {WIS), No. 3. pp. 200- 

 206. pis. 7). — Investigations begun by the author in 1917 on possible control 

 methods for citrus canker have yielded data which are here presented in 

 tabular form, with discussion to supplement the observations recorded by 



