CONTROL OF PEACH BACTERIAL SPOT. 7 



same amount of pruning and cultivation and received throughout the 

 two years exactly the same treatment except as to the fertilization 

 outlined in these experiments. It is evident, therefore, that the 

 striking differences noted were due to the nitrate of soda alone. The 

 larger amount of infection on the trees of all plats growing next to 

 the meadow, upon which the grass was encroaching, indicates that 

 cultivation was generally beneficial to all the plats. Kolfs, 1 in Mis- 

 souri, obtained good results in the control of this disease by means of 

 cultivation, pruning, and the use of nitrogenous fertilizers. In those 

 regions of the South in which the disease has been serious, nitrogen 

 appears to be the most deficient of the important plant-food 

 materials. 2 



These experiments indicate that, at least in the South, peach 

 orchards which are kept in good growing condition are not liable to 

 suffer from the disease to any serious extent. Proper pruning, cul- 

 tivation, and fertilization so increase the resistance of the trees that 

 the causal organism is unable to attack them successfully. 



Pruning, besides benefiting the tree in general, may also remove 

 many of the twig cankers in which the bacterium passes the winter, 

 thus eliminating many of the sources of infection. 



SUMMARY AND CONCLUSIONS. 



(1) The peach bacterial spot, also known as bacteriosis, caused 

 by Bacterium pruni, occurs in practically all peach-growing regions 

 of the eastern half of the United States. It is most serious in the 

 more southerly parts of this region. Bacterium pruni also causes a 

 disease of the plum, affecting especially the Japanese varieties. 



(2) Twigs, fruit, and leaves are affected, but the most serious 

 injury is to the leaves. 



(3) Experiments carried on by the writer and others indicate that 

 the disease may be kept in check in southern peach orchards by 

 proper pruning, cultivation, and especially fertilization. Nitrate of 

 soda was by far the most efficient fertilizer used. Trees in which a 

 high state of vigor and health is maintained are commercially 

 resistant to the disease. 



1 Op. cit. 



2 For a discussion of peach tillage and fertilization, see Gould, H. P. , Growing peaches : Sites, propagation, 

 planting, tillage, and maintenance of soil fertility, U.S. Dept. Agr., Farmers' Bui. 631, 24 p., 7 fig. 1915. 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1917 



