106 MASS. EXPERIMENT STATION BULLETIN 252 



Bordeaux 4-4—50 was employed as a standard, and basic copper sulfate 

 without adhesive as a check. The amount of copper in the unwashed 

 spray residue was fairly constant and averaged 0.0091 grams to 100 square 

 inches. Basic copper sulfate with and without adhesive deposited sub- 

 stantially as much copper as Bordeaux. The results after washing are 

 less dependable, however, as washing was a factor impossible to control 

 under the conditions of the experiment. Bordeaux is fairly conspicuous 

 on the leaf surface due to the excess lime (whitewash). Guba reported 

 the retention as "excellent", which was confirmed by the copper content. 

 Basic copper sulfate is less visible. The adherence was reported as "poor 

 to fair", although the copper was two-thirds that of Bordeaux. Admix- 

 tures with flour, Wilkinite and other substances increased the visibility of 

 the residue. Sugar with basic copper sulfate was "poor" and actually 

 reduced adherence, probably due to the formation of copper saccharate 

 which is removed by washing and carried more or less of the insoluble por- 

 tion of the fungicide. Guba employed 0.05 per cent of dextrin with basic 

 sulfate on cucumbers and celery in the field but did not observe any in- 

 crease in either spreading or adhesiveness. Flour proved a "good" adhe- 

 sive, and Tekoe "fair to good" at both concentrations. The efficiency of 

 both products might have been increased by the addition of a small 

 amount of alkali to disperse the albuminous compounds. Gum arabic was 

 "poor to fair" and saponin "poor." 



Glue was reported "fair to good", but was more promising in field tests 

 than the figures indicate. Laucksite, a soy-bean-fish-oil adhesive, was 

 effective but disliked and is not obtainable in eastern markets. Skim milk 

 powder was "poor"; semi-solid buttermilk, reported "fair to good", was 

 ineffective; and calcium caseinate of similar character. Better dispersion 

 might have proved of advantage. Castile soap increased adherence. Ivory 

 scap was "fair to good"; and rosin fish-oil soap, reported "fair", was of 

 little value as an adhesive, although 0.75 per cent (1 ounce per gallon) 

 in field tests proved superior to 0.10 per cent glue. Wilkinite increased 

 visibility but not adhesiveness. 



Linseed oil, at the rate of 0.10 per cent, with basic copper sulfate has 

 been employed in field experiments with various crops for two seasons. 

 The oil disperses readily in the spray and seems to have value as a sticker. 

 Its use on fruits has been endorsed by some members of the staff. 



• In Guba's experiments the addition of a small amount of properly dis- 

 persed flour, glue and Castile soap to basic copper sulfate, evidently in- 

 creased the adherence, but whether this was due to better distribution, to 

 the formation of more resistant deposits, or both, is difficult to say and 

 likely to vary with the supplement employed and the character of the 

 leaf surface. Reaction products such as copper albuminate, caseinate, 

 oleate, palmitate, resinate, stearate and tannate are relatively insoluble in 

 water and are generally considered of low fungicidal value, but in small 

 amounts may increase the retention of the deposit on the leaves. Fineness, 

 stability and water-resisting properties are factors to be noted. Various 

 proprietary Bordeaux mixtures and copper hydroxide might profit by simi- 

 lar treatment. The time and labor required for the proper dispersion of the 

 adhesive, however, is a feature that renders the process objectionable to 

 most operators. 



