388 Bulletin 164. 



shoots growing out beyond the region covered by the spraying 

 were wholly free from such injuries. There was no doubt that this 

 general appearance of a shot-hole fungus on the Japan plums was 

 due directly to the spraying. An unsprayed orchard of Burbank 

 and Abundancein the vicinity showed no shot-holein j ury whatever. 



Later experiments on the Chabot plum confirmed the previous 

 work, indicating that under certai-n conditions the Bordeaux mix- 

 ture may be injurious to the foliage of the Japan plums, much 

 more so, in fact, than to that of the peach. 



Among the varieties which have shown the greatest injury from 

 spraying during the past season may be mentioned, Willard, 

 Chabot, Douglass, Berckmans, Earliest of All, Georgeson, Ogon 

 Kelsey, Blood No. 3, and Abundance. Burbank and Red June 

 were also affected. Forest Garden was the only native plum 

 noticeabl}^ affected, and all varieties of the domestica group were 

 conspicuously free from the trouble. 



An examination of specimens of the various fungi affecting the 

 peach and the plum will show that, with the exception of leaf- 

 curl, mildew% and a few others, these fungi are very generally 

 productive of a shot-hole effect. The fungus most abundant in a 

 particular region will be the one there designated as a shot-hole 

 fungus. With these facts at hand, my experiments w4th fungi- 

 cides and other chemical agents above referred to were made. 

 These results are sufficient to demonstrate that this shot-hole 

 effect is a peculiar ph\\siological reaction of the plant to injuries 

 of many kinds. 



Figure 72 shows an effect of this kind produced by peculiar 

 causes. The tree w^as blown dowm during a summer rain storm. 

 The rain was followed by a hot, steaming afternoon; and in about 

 two days the shot-hole effect was evident. 



After an examination of a number of plum orchards in this 

 State, I find the Japan plums so free from shot-hole fungi that I 

 see no necessity of spraying them for these particular diseases 

 and thus encouraging a shot-hole effect due to spra3dng. 



Where the plum rot is bad, it will be necessary to spray, and one 

 must disregard the slight injuries to the foliage resulting from 

 the use ofproperly made Bordeaux mixture. 



B. M. DUGGAR. 



