Peach Leaf-Curl. 379 



because the fungicides themselves often injured the leaves, and 

 also because the best time for spraying was not apparent from our 

 knowledge of the fungus. Much of the later work has been to 

 demonstrate that spraying one season lessons the disease during 

 the succeeding season. At the time that my experiments were 

 begun, I was not aware of other results. 



In an orchard of young trees closely set and used for some 

 experiments with borers, by M. V. Slingerland, leaf-curl appeared 

 in 1896. The following year it was so abundant as to cause 

 almost entire defoliation, and there was every promise of an 

 abundant reappearance of the disease in 1898. These trees were 

 so close together that they were especially desirable for such 

 work, since it would be very probable that any remedy proving 

 more or less effective under such conditions would be even more 

 effective under ordinary circumstances. There was also the addi- 

 tional advantage that the trees were all known to have been 

 affected the previous year. Several varieties were represented in 

 the orchard, and the experimental rows were run across varieties, 

 so as to eliminate any error on this score. 



The treatments given, and dates of spraying, were as follows :* 



Row 1. Check. 



2. Bordeaux mixture, April 8, May 10, May 21, June 8. 



3. Bordeaux mixture. May 10, May 21, June 8. 



4. Bordeaux mixture, April 8, Potassium sulfide, May 10, 

 May 21, June 8. 



5. Check. 



6. Potassium sulfide. May 10, May 21, June 8. 



7. Bordeaux mixture, April 8, Amnion, copper carbonate, 

 Ma}^ 10, Ma}^ 21, June 8. 



8. Amnion, copper carbonate, May 10, 21, June 8. 



In the statement of results the abundance of the disease the 

 previous year must be remembered, for it is very evident that no 

 hope could be entertained for securing exemption from the 

 disease where the fungus had been carried over winter in 

 the twigs. 



* In this experimental work Mr. H. P. Gould cooperated with me. 



