436 MANUAL OF FRUIT DISEASES 
same way, except that the amounts of copper-sulfate and lime 
are varied according to the requirements. 
Copper-sulfate. 
This salt alone may be used only in very dilute solutions on 
foliage and fruit, and as a summer spray has but few uses. 
As a disinfectant for dormant peach trees it may be used as 
strong as necessary and is very effective against peach leaf-curl. 
Copper-sulfate, 1 Ib. ; water, 15-25 gal. Dissolve the copper- 
sulfate in the water. It is then ready for use. One pound 
in twenty gallons of water has been found effective against 
the above named disease. 
Lime-sulfur solution. 
The fungicidal value of lime-sulfur was discovered in America 
about 1880 when California peach-growers using it on dormant 
trees for the San José scale found that it controlled the leaf- 
curl. As a matter of interest it may be noted that several 
years earlier a boiled solution of lime and sulfur much diluted 
was in use by European gardeners as a fungicide on growing 
plants. Its use was, however, not general and its possibilities 
were disregarded or overlooked in the general belief that the 
newly discovered bordeaux mixture was of universal applica- 
tion. The-re-discovery of lime-sulfur as a summer spray about 
1906 by Cordley of Oregon marks the beginning of a new epoch 
in the history of fungicides. 
The fungicidal properties of lime-sulfur reside in the sulfur 
or, more accurately perhaps, in the sulfuric acid which is even- 
tually formed by the oxidation of the sulfur in the presence of 
water. The special virtue of the lime-sulfur solution (poly- 
sulfides of calcium) lies in the fact that after evaporation of the 
water they are gradually oxidized, leaving pure sulfur in exceed- 
ingly finely divided particles on the sprayed surface. Injury 
by lime-sulfur usually occurs as the solution dries, and especially 
where the trees have been drenched. Large quantities of the 
solution are left along the curved edges of the leaves, where as 
