286 BULLLTIN 164. 



had been abundantly sprayed. From observations already made, 

 I had suspected that other causes besides the shot-hole fungus 

 might be responsible for some of the troubles referred to me. In 

 one case, especially, there was an unusual appearance of the 

 shot-hole effect in a large orchard soon after the application of 

 Bordeaux mixture. 



On the horticultural grounds of the Experiment Station, during 

 the season of '97, Mr. H. P. Gould called my attention to the 

 abundance of the shot-hole effect on Japan plums which he had 

 sprayed constantly. I had then completed some experiments 

 with the production of such injuries bj^ means of substances 

 injurious to the foliage; and the results indicated clearly that 

 injuries to the foliage by many deleterious chemical agents might 

 produce the characteristic shot-hole appearance. 



It was reasonable to believe that spraying might have the same 

 effect under certain conditions. • Later experiments were made to 

 test the effect of some copper compounds upon the foliage of the 

 peach and of the apricot, and comparatively upon plums of the 

 native, domestica, and Japan groups. In general the peaches, 

 apricots, and plums of the native and domestica groups were free 

 from any shot-hole effect ; but the Japan plums generally indi- 

 cated some injuries of this kind. The entire orchard had been 

 sprayed with Bordeaux mixture tested with potassium ferro- 

 cyanide. A few trees of each kind mentioned were then sprayed 

 with properly prepared Bordeaux mixture, with Bordeaux mix- 

 ture containing an excess of copper, with Bordeaux made b}^ the 

 use of poor lime, and with a solution of copper sulfate containing 

 one pound of the compound to about 15 gallons of water. 



The properly prepared Bordeaux produced no injury except 

 upon the Japan plum (Burbank) ; but there was an evident injur}^ 

 in the latter case. The improperly- made Bordeaux mixtures affect- 

 ed the peach and the Japan plum to a marked extent, a photograph 

 of injuries to the latter being shown in figure 71. By the same 

 mixture the apricot and the native plum (Yellow Transparent) 

 w^ere somew^hat injured, while the effect upon the domestica 

 (Empire) was scarcely noticeable. The copper sulfate solution 

 of course produced injury in all cases, but this injury was very 

 little in the case of the domestica, and somewhat more pro- 



