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. Rolfs, 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. 
i 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 OFFICII] : 1917 
