50 A[ASS. EXPERIMENT STATION BULLETIN 378 



been obtained on bog No. 3 in other years; although this bog has been 

 found, through experiments extending over a period of years, to be one 

 on which the control of rot is very difificult. Judging from results obtained 

 this year on bog No. 3, cuprocide-bentonite 4-5-100 appeared to be slightly 

 superior to bordeaux 10-4-100 for rot control. Cuprocide-bentonite 3-4-100 

 on section 8 of the State Bog gave as good control of rots as did bor- 

 deaux 10-4-100. Yellow cuprocide 1-100 on section 14 of the State Bog 

 had little eflfect in reducing rot. Basic copper arsenate 4^-100 also ap- 

 pears to be ineflfective since on section 8 of the State Bog it reduced the 

 rot, up to December 1, very little in comparison with untreated plots. 

 Yellow cuprocide I1/2-IOO, as shown by the results on Bog No. 9 where 

 fruit rots were controlled most efifectively by bordeaux 10-4-100 and by 

 basic copper arsenate 6-100, seems definitely to be less eflfective than 

 bordeaux for rot control. The results obtained with yellow cuprocide 

 2-100 and with basic copper arsenate 6-100 are not conclusive. Basic 

 copper arsenate on bog No. 9 gave as good control of fruit rots as did 

 bordeaux 10-4-100. On bog No. 3 neither yellow cuprocide 2-100 nor basic 

 copper arsenate 6-100 reduced the amount of rot, up to December 1, as 

 compared with that in berries from nonsprayed plots and basic copper 

 arsenate appears even to have increased it. 



Blueberry Disease Investigations. (H. F. Bergman.) Severe defolia- 

 tion and dying-back of twigs and small branches, and sometimes also of 

 main branches, was observed in two blueberry plantings in each of which 

 from six to twelve bushes were affected. Phomopsis was isolated from ma- 

 terial from both plantings. This fungus heretofore, except in the case of 

 two bushes in the State Bog planting reported last year, has not been 

 known to cause greater injury than the killing of the tips of twigs. 



DEPARTMENT OF DAIRY INDUSTRY 

 J. H. Frandsen in Charge 



The Cacao-Red or Tannin-Like Substances in Commercial Cocoa Pow- 

 ders. (W. S. Mueller cooperating with Control Service — J. W. Kuzmeski 

 and A. F. Spelman.) Since it seemed possible that the cacao-red (tannin- 

 like substances) in cocoa might be one cause of the observed decrease in 

 growth rate of white rats when excessive amounts of cocoa were added 

 to milk, the first step in the investigation was to analyze commercial 

 cocoa powders for cacao-red. Authorities do not agree on the chemical 

 composition of cacao-red and most of the methods of analysis are rather 

 crude and somewhat unreliable. Ulrich's method was used in this study 

 because it is the generally accepted method. By this method the amount 

 of cacao-red in cocoa is reported as weight of the insoluble iron com- 

 pound. Sixteen samples of commercial cocoa powders have been analyzed 

 and values for the iron precipitate ranged from 2.62 to 15.59 percent, with 

 an average of 10.83 percent. In general, unprocessed cocoa was found 

 to have a higher cacao-red content than the processed cocoa. 



It was thought that Ulrich's method could be improved by investigating 

 the composition of the insoluble iron compound. Accordingly, the Con- 

 trol Service has analyzed the insoluble iron precipitate obtained from 

 various samples of cocoa powder. The following analysis is typical for a 

 number of samples: 



