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 
Fic. 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. 
FoRMULZ 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- 
