PEAR DISEASES 



1617 



degree of confidence. It was well known 

 at this time that certain human diseases 

 were caused by bacteria, but most bac- 

 teriologists were quite unwilling to think 

 that vegetables could be invaded by germ 

 life. 



Dr. Burriirs announcement of the bac- 

 terial nature of pear blight was not ac- 

 cepted until Dr. J. C. Arthur confirmed 

 it by a series of brilliant experiments 

 which were made during the seasons of 

 1884 and 1885. His results were pub- 

 lished in the proceedings of the Ameri- 

 can Association for the Advancement of 

 Science, for the year 1885. This paper 

 was read at Ann Arbor, Michigan, in 

 1885, and produced a great sensation. 

 Although Dr. Burrill discovered the true 

 nature of the pear-blight disease, the 

 work of Dr. Arthur was needed in order 

 to give Dr. Burrill's theory credence in 

 this country. After Dr. Arthur's paper, 

 no man had any doubt as to the nature 

 of pear blight; at least, no scientific man. 



That Dr. Burrill's discovery was doubt- 

 ed by many eminent men should cause 

 little wonder, because at that time there 

 were fewer advantages and fewer labora- 

 tories equipped for scientific research 

 than there are now. Even at that time 

 the great Dr. Koch, the eminent German 

 authority on tuberculosis, had not yet 

 discovered the cause of this disease. 

 However, since the initial discovery of 

 the bacterial nature of the pear-blight 

 disease, investigation of its nature and 

 the life history of the germ have pro- 

 ceeded along the lines of modern bacteri- 

 ological methods until at the present 

 time we have as complete a knowledge 

 of the pear-blight germ as the doctors or 

 physicians have of the typhoid germ or 

 germ of tuberculosis. In the spring of 

 1889 Professor M. B. Waite, pathologist 

 of the United States Department of Agri- 

 culture, was assigned the task of investi- 

 gating the pear-blight disease. At the 

 time when he began his work, while the 

 disease was known to be of germ origin, 

 the life history of the germ was not 

 known. No one had yet found out where 

 the germ remained during the dormant 

 period of the trees; that is to say, during 

 the fall and winter. It had been sup- 



posed that the germ lived in the soil or 

 in swamps, if such were near by, and 

 that during the spring when the blossom- 

 ing season began these germs were blown 

 by the winds into the blossoms, and in- 

 fection again started. Professor Waite, 

 after an enormous amount of experi- 

 mentation, found that the germ did not 

 live in the soil; furthermore, he found 

 that it did not blow about in the winds, 

 but that the germ lives during the dor- 

 mant period of the tree in "cankers," pro- 

 duced by the germ during the growing 

 season. 



In the Eastern states pear blight has 

 done an enormous amount of damage in 

 the past, more so than the Pacific Coast 

 orchardists realize. In fact, one of the 

 reasons for the commercial success of pear 

 growing on the Coast has been the difii- 

 culty or inability of growing the better 

 varieties of pears in the face of attacks 

 by this disease in most sections of East- 

 ern states. During the past fev/ years 

 pear blight has been very serious in New 

 York, Michigan and generally through- 

 out the East. The same may be said of 

 the Southern states, such as Georgia and 

 Florida. Usually, blight has been less 

 severe in Michigan and New York, espe- 

 cially in the cooler, more damp sections 

 in the vicinity of the, Great Lakes; how- 

 ever, in Niagara county. New York, 

 which borders on Lake Ontario, there 

 have been serious epidemics of pear 

 blight There are many Bartlett pear 

 orchards throughout the northern por- 

 tion of the Eastern states, but southward 

 of this, Bartlett pear growing Is almost 

 abandoned. The Oriental pears are more 

 resistant and more adapted to the cli- 

 matic conditions in the South, and hence 

 are grown quite extensively, or were at 

 one time. Within the past few years the 

 Le Conte and KiefCer varieties, grown 

 principally in Georgia and Florida, have 

 been practically wiped out by pear blight. 

 At one time these varieties were shipped 

 into New York from the South by the 

 trainload. Apples have also suffered to 

 a very great extent, although, as a rule, 

 in the commercial sections of New York, 

 New England and Michigan but little 

 damage has been done. Occasionally 



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