4 BULLETIN 543, U. S. DEPARTMENT OF AGRICULTURE. 



bility of different varieties,- but the Bilyeu, Elberta, Carman, Cham- 

 pion, Oldmixon, Sneed, and Waddell appear to be more susceptible 

 than such varieties as the Hiley, Belle, Fox, Edgemont, Rivers, Early 

 Crawford, and Salway. Rolfs 1 gives an extensive list of varieties, 

 with estimates as to relative susceptibility and resistance. All 

 varieties were found by him to be susceptible to some extent. 



CONTROL EXPERIMENTS. 



It was not until 1913 that the problem of control came directly 

 before the Bureau of Plant Industry. During that year one section 

 of an orchard in the Ozark region of Arkansas in which spraying 

 experiments for the control of brown-rot and scab were being con- 

 ducted suffered severely from an attack of this disease. Twigs, leaves, 

 and fruit were badly infected, and no control by the spraying was 

 apparent. It may be said both from the experiments of this bureau 

 and from those of Rolfs * that the sulphur mixtures (not lime-sulphur 

 solution) , which are the only known fungicides that can be used with 

 safety on the peach during the growing season, will not control this 

 disease. In Georgia in 1909 the writer noticed that trees which were 

 in good growing condition, that is, which had been well pruned, 

 fertilized, and cultivated, were practically free from the disease, 

 whereas those which had been allowed to go without pruning, fer- 

 tilization, and cultivation were to a considerable extent damaged 

 by the disease. Similar observations were made in Georgia in 1912, 

 but the disease did not then appear to be of sufficient importance 

 to demand experiments in control. 



When, therefore, in 1913 it seemed desirable to work out proper 

 means of control, the first things that suggested themselves were nat- 

 urally pruning, fertilization, and cultivation. The writer's observa- 

 tions were further supported by a statement in the report of the 

 Director of the Missouri Agricultural Experiment Station for 1912 2 

 to the effect that in the case of winter-injured trees the plats fertilized 

 with nitrogen were nearly free from the bacterial disease, while in 

 adjacent unfertilized plats the damage was very great. 



During the seasons of 1914 and 1915 the same orchard in which 

 the spraying experiments had been conducted in 1913 was used 

 for experimental work in the control of bacterial spot. This orchard 

 consisted of a block of Elberta trees which was bounded on one side 

 by a road, on the second side by a cultivated field, on the third side by 

 a meadow, and on the fourth side by an apple orchard. The disease 

 had been particularly severe in the corner adjacent to the meadow 

 and the apple orchard. Accordingly, the experiments were con- 



> Op. Cit. 



2 Mumford, F. B. Fertilizing peach trees. In Mo. Agr. Exp. Sta. Bui. Ill (Rpt. [1911J12), p. 247-248, 

 1913. 



