SUPPLEMENTS FOR COPPER FUNGICIDES 103 



O.IO per cent of sugar or 0.05 to 0.15 per cent of dextrin no improvement 

 was observed. With 0.10 to 0.21 per cent of Tekoe flour a sligiit increase 

 was reported and with 0.10 per cent of wheat flour "fair" spreading ob- 

 tained. Starchy products have to be dispersed (gelatinized) before use, 

 and in the case of flour and its by-products the addition of dilute caustic 

 soda or potash probably increases their effectiveness by dissolving the 

 proteids. Alkali was not employejl in this experiment. With 0.05 to 0.15 

 per cent of gum arable (Acacia) poor wetting and spreading were secured, 

 which probably holds true for tragacanth. 



Soapbark (Quillaja) extract and 0.03 to 0.10 per cent of technical 

 saponin gave excellent spreading. Guba did not commend either gelatin 

 or soluble albumen at the rate of 0.05 to 0.10 per cent but obtained ex- 

 cellent wetting and spreading with the same amount of glue. Gelatine 

 and glue have to be dispersed in warm water, and a high-grade animal 

 glue requires aging to develop its maximum efficiency as an adhesive. 

 Possibly a low-grade animal glue which is more readily soluble or a fish 

 glue might serve in this connection, although there is no evidence to that 

 eft'ect. Albumen, casein, dried blood, egg-powder and other nitrogenous 

 substances require a small amount of alkali for proper dispersion. With 

 0.10 per cent of skim milk powder, good spreading was secured; but an 

 equivalent amount, in dry matter, of semi-solid buttermilk proved less 

 satisfactory and about equal to Tekoe flour. No alkali was added. With 

 0.10 to 0.13 per cent of calcium caseinate, a commercial preparation, ex- 

 cellent wetting and spreading were obtained. Laucksite, a soy-bean^fish- 

 oil adhesive, proved less satisfactory. With 0.10 per cent of Castile soap, 

 0.10 per cent of Ivory soap and 0.05 to 0.75 per cent of rosin fish-oil soap, 

 excellent spreading was secured — even better in the case of rosin fish-oil 

 soap than with calcium caseinate. The resulting curdy precipitate on 

 standing was objectionable with all soaps. Soaps are effective on both 

 plain and waxy surfaces, although the amount may have to be increased 

 to 0.20 to 0.25 per cent in the latter case. With 0.10 per cent of Wilkin- 

 ite poor wetting and spreading were obtained. 



In Guba's experiments saponin, glue, calcium caseinate and soap proved 

 the most efficient of the substances tested, although wheat flour deserves 

 mention. Some albuminous substances may react with the copper to form 

 soluble compounds as previously shown (Sec. 1). Soap mixtures should 

 be appjied immediately after preparation to avoid the formation of a 

 curdy precipitate. The cost of most of the supplementary products is 

 negligible as compared with labor, but the reduction in amount of infec- 

 tion due to better distribution of the fungicide is not always appreciable 

 according to our Station observers. This may not hold equally true on 

 waxy surfaces. 



4. To increase adhesiveness by forming more resistant deposits. 



The degree of dispersion and uniformity of distribution are important 

 factors in the adhesiveness of copper fungicides. An increase in spread- 

 ing assures better distribution and generally a more persistent and pro- 

 tective deposit. Many investigators endeavor to increase adherence still 

 further by the formation of more resistant deposits. If carried too far, 

 however, the fungicidal action may be impaired and the physiological ac- 

 tivity of the plant reduced materially by the impenetrable coating on the 

 surface which is particularly noticeable in the case of certain emulsions. 



