266 



CALIFORNIA FRUITS: HOW TO GROW THEM 



rich valley land which it traverses and on which is situated our 

 most extensive pear acreage. In 1905 resolute warfare was made 

 upon the blight, with a large appropriation of State funds, by the 

 plant disease experts of the United States Department of Agricul- 

 ture and the California Agricultural Experiment Station, with 

 the assistance of the local horticultural authorities. It was probably 

 the greatest campaign ever made against a single tree disease, 

 although some insect warfares have been greater. The outlines of 

 the plans followed and the results attained are to be found in the 

 publications of the institutions engaged.* 



Detailed information concerning the treatment of blight as indi- 

 cated by progressive research and experimentation is also to be 

 had from these institutions and from California horticultural 

 journals which record the latest methods and results by pear 

 growers who are continually introducing new methods of applying 

 the only treatment thus far found effective, and that is cutting out 

 and burning the affected parts. The cutting must be below the 

 parts seen to be diseased, even to the roots of the tree, and dis- 

 infecting the tools used in one cut before again cutting into the 

 tree.f 



It is usually best, unless one is thoroughly acquainted with the 

 disease, to submit specimens of suspected blight to the University 

 Experiment Station at Berkeley, for a beginner may be easily 

 deceived. However, that the inexperienced person may have a 

 general idea of what to look for, the following outline of symptoms 

 is given : 



The most obvious effect of blight to be seen during the growing season, 

 is the blackening of the leaves and soft wood to which they are attached, 

 as though these parts had been touched by a flame, and from this appear- 

 ance comes its old common name, "fire-blight." More specifically, as Prof, 

 R. E. Smith has written, the leaves, blossoms and young fruit wither and 

 turn black on the affected portions but do not fall, remaining tightly at- 

 tached to the twigs during the winter after the healthy leaves have fallen. 

 The infection proceeds downwards through the inner bark of the twigs 

 and branches, and when working vigorously the blight kills the twigs or 

 whole branches very rapidly. The disease often runs down into the large 

 limbs, where it remains alive over winter, producing the so-called "hold- 

 over" blight, which is a source of infection during the following season. 



The blighted twigs, branches or trunks show a red, sappy, juicy con- 

 ff 110 * 1 f the inner bark when infected with the true pear blight organism. 

 If the disease is fresh and active the bark when cut into is very juicy, ex- 

 uding the slightly sticky sap quite freely and showing bright red color in 

 Jhe inner bark. This symptom is of importance in distinguishing true 

 blight from such troubles as die-back from sour sap, crater blight and 

 other causes. 



In the smaller twigs and branches the organism dries out and becomes 

 entirely dead. But, through the agency of biting insects in the young 

 shoots and suckers, the disease frequently gets into the trunk of the tree 

 and also down into the roots. Here it spreads and causes the death of 



*Report8 of the California Commissioners of Horticulture, 1901 to 1906, including 

 Reports on California Fruit Growers' Convention for 1905-6-7, Horticultural Commissioner, 

 and^rJog 110 ' P rt f Plant Path lgist, University Experiment Station, Berkeley, 1906 



tThe character of such a fight and what it costs is graphically portrayed by E. A. 

 ammon m the Report of California Fruit Growers' Convention of 1909, and in Pacific 

 Rural Press, June 22, 1910. 



