650 EXPERIMENT STATION RECORD. [Vol. 36 



No organism was found to cause the disease. It is believed that a lack of 

 moisture during the preceding fall and winter had caused the smaller roots to 

 dry and die. Alter the trees had put out their leaves and formed fruit, the 

 increasing dryness of the air made such demands for water that death of the 

 tree resulted. 



[Reports on grape downy mildew] (Rev. Vit., 44 (1916), Nos. 1125, pp. 64- 

 66; 1127, pp. 97, 98; 1128, pp. lU-117 ; 1129, pp. 121-134; 1130, pp. 137-156).— 

 This continues an account of reports from various sections on downy mildew, 

 as made in 1915 and noted previously (B. S. R., 35, p. 352). This is considered 

 the most important body of information yet collected on this subject, on 

 account of the extent of territory involved and the number, scope, and charac- 

 ter of the responses made to requests for information, as noted below. 



The development and the treatment of downy mildew in 1915, J. Capus 

 (Rev. Vit., U (1916), Nos. 1131, pp. 157-162; 1132, pp. 181-190, figs. 2; 1133, 

 pp. 201-206, fig. 1; 1134, PP- 217-224; 1135, pp. 237-247, figs. 2; 1136, pp. 253- 

 255; 1138, pp. 289-303; II40, pp. 325-334, figs. 2; II4I, pp. 341-350; II42, pp. 

 357-363; abs. in Compt. Rend. Acad. Agr. France, 2 (1916), No. 22, pp. 619- 

 621). — Analyzing the large body of information which is noted above, the 

 author gives a compact summary of certain portions with some practical con- 

 clusions as deduced therefrom. 



It is stated that in spite of the exceptional severity of attacks and of the 

 economic situation in 1915, a number of vine growers were able to save their 

 crops largely or entirely. As in previous years, the preservation of the vines 

 as against mildew was found to depend upon such circumstances as the time 

 of treatment, the proportion of copper employed, and the care used in spread- 

 ing the fungicides, among which first rank was held by Bordeaux and Burgundy 

 mixture and copper acetate solution. 



As usual, there was a period of a few days just previous to the outbreak 

 during which the treatment could be applied with assurance of its absolute 

 efficacy. This favorable period is related, in case of a primary outbreak, 

 to a period of precipitation. Secondary invasions are related to a rain or 

 period of precipitation following a primary invasion. The determination and 

 utilization of a period favorable for treatment requires the services of a 

 specialist for each region, and its efficacy also depends upon the carefulness 

 and thoroughness of its employment. 



In the absence of such special information, a fair degree of success has 

 been attained by thorough and careful spraying each time that the conditions 

 led to new growth of the vines. Protection of the grapes requires very careful 

 spraying during the period of inflorescence. The duration of effectiveness of 

 the spray Is dependent largely upon the abundance of the spray and upon its 

 copper content. With the exception of certain cases, in which a 1 per cent 

 solution appears to be effective, a strength of 2 per cent Is considered to be 

 the lowest that is safe, at least for general practice, especially in years when 

 conditions are such as to favor serious outbreaks, as in 1910 and 1915. For 

 infrequent treatment or late final treatment, a strength of 3 per cent is con- 

 sidered preferable. 



Casein is the only material that has up to this time been extensively used 

 in ordinary practice to increase the adherence of the fungicides, but the 

 results from this are said to be satisfactory. Copper fungicides in the form 

 of powders are reliable as regards fungicidal results, when employed at a 

 favorable time. They are not so lasting as are the sprays, but they cause 

 less injury to the fruits. A number of viticulturists employ powdered prepa- 

 rations Immediately following the spray. No general superiority of acid 



