434 MANUAL OF FRUIT DISEASES 



membranes dry down and attach themselves like glue to the 

 surface. When wetted by dew or rain, they swell but do not 

 dissolve slowly. The action of the moisture and the air is to 

 free a portion of the copper in the membrane which acts on the 



i 



FIG. 124. Bordeaux-injury on apples. 



germinating spore to inhibit its growth or to kill it. Injury 

 by bordeaux (Fig. 124) results when weather conditions favor 

 excessive solution of the copper from the membranes. 



FORMULAE FOR PREPARATION 



Bordeaux mixture. 



The standard formula for use on fruit is usually a 5-5-50 or 

 a 3-3-50 mixture, that is, 5 pounds quick-lime, 5 pounds copper- 

 sulfate crystals, and 50 gallons of water ; or if a weaker solution 

 is desired, 3 pounds quick-lime and 3 pounds copper-sulfate 

 to 50 gallons of water. In general, it is best to prepare stock 

 solutions of the lime and of the copper-sulfate from which the 

 bordeaux mixture may be prepared later as needed. To pre- 



