CHAPTKR IV. 



PLAN OF PREVENTIVE SPRAY WORK CONDUCTED BY THE 



DEPARTMENT. 



PRELIMINARY PLANS FOR THE WORK. 



The partial control of peach leaf curl in the sprinjjfof 185>8, in a few 

 orchards of the Sacramento Valley in which the trees had n'ccived a 

 winter spraying for the control of the San Joso scale {AxpidlotiiK per- 

 niciosuis)^ showed to the writer the importance of conducting careful 

 experiments for the prevention of curl. As a foundation for experi- 

 mental work a circular of inquiry was sent to some 1,500 peach growers 

 of the United States in the fall of 18J>8. The facts thus obtained were 

 of much value, but the general lack of accurate know ledge respecting 

 both the nature and control of the disease, as well as the heavy losses 

 reported from this cause in different sections of the country, strikingly 

 emphasized the need for widespread and thorough pre\'entive experi- 

 ments. 



After careful consideration it was concluded to inaugurate two series 

 of experiments. The first, which had been planned before the sending 

 out of the circular, was to be conducted in California under the direct 

 supervision of the writer, and the second, planned somewhat similarly, 

 though on a more limited scale, was to be carried out by the growers 

 themselves in various peach-growing sections of the country. The 

 personally conducted work is described here, while the results of the 

 cooperative work are given farther on. 



Observation and correspondence had already shown which sections 

 of California were most subject to frequent and serious recurrences of 

 the disease. Facts thus gathered led to the opening of correspondence 

 with Mr. George F. Ditzler, the manager of the Rio Bonito orchard, 

 situated in the Sacramento Valley, in the bottom lands of the Feather 

 River, near Biggs, Cal. This orchard is the property of the Hatch & 

 Rock Orchard Company, and comprises some 1,600 acres, several 

 hundred of which have as fine peach trees as any in the State. Among 

 the varieties of peaches in this orchard is a large acreage of Lovell 

 trees. The Lovell, it was learned, while presenting as thrifty growth 

 as any variety in the orchard during years when curl did not prevail, 

 had been especially subject to it in seasons favorable to its develop- 

 ment, the crop of this variety, which would amount to several 



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