TWENTY-FIRST ANNUAL MEETING 201 



Sulphur-Arsenical Spray Injury and Its Prevention. 



By Dr. J. P. Stewart, 

 Experimental Pomologist, State College, Pennsylvania. 



The recent extensive use of lime-sulphur solutions in 

 ■combination with the ordinary lead arsenates as a summer 

 spray has placed an unusual strain on the materials and has 

 resulted in extensive and apparently increasing complaints 

 of injury. During the past season such complaints have 

 been heard or the injuries observed by the writer in several 

 states, and in some important fruit sections, the growers 

 now seem more at a loss as to how to spray their trees than 

 -ever before. In each of the past two years, certain cases 

 amounting to practical ruination of apple or peach crops 

 have come to our attention, and in some instances even the 

 trees have been killed. In spite of these striking cases, 

 however, the total injury from lime-sulphur is probably 

 much less than that from an equal amount of spraying with 

 Bordeaux. But is is quite important that the danger be 

 appreciated and guarded against by such precautions as we 

 are now able to ofter. 



These precautions are based primarily on the results of 

 tests and experiments conducted at the Pennsylvania sta- 

 tion for the past three years. During the first year we 

 tried to determine what dilutions of lime-sulphur alone 

 could be safely used on the foliage of various fruits. Dur- 

 ing the past two years we have studied the effects of com- 

 bining lime-sulphur with various kinds of arsenicals. The 

 latter experiments were confined almost entirely to the 

 peach, largely because of its greater sensitiveness to spray 

 injury. Contrary to certain results reported elsewhere, our 

 combined sprays have resulted practically uniformly in 

 g'iving more injury than was obtained from applications of 

 lime-sulphur alone. The lime-sulphur used was made by 

 the method advised in our bulletins and hence was known 



