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ENCYCLOPEDIA OK PRACTICAL HORTICULTURE 



but in the earlier accounts the conclu- 

 sions concerning the cause of the disease 

 are erroneous. The earliest record we 

 have of pear blight was published in the 

 "Transactions of the Massachusetts So- 

 ciety for the Promotion of Agriculture," 

 in 1794. This report contains a letter 

 written by William Denning, December 

 22, 1793. He first saw the disease on the 

 highlands of the Hudson in 1780. He 

 also noted that, besides attacking apples, 

 the malady also affected pears and 

 quinces. Subsequently, others reported 

 its occurrence on Long Island and in 

 New Jersey and Pennsylvania in the 

 vicinity of Philadelphia. It also seems 

 to have appeared quite general in the 

 apple and pear orchards in the Eastern 

 states, and following the settlements in 

 Oliio, Indiana, Michigan and Illinois we 

 find that the pear blight appeared and 

 attacked the young pear and apple or- 

 chards. It was also well known that the 

 disease occurred on wild crabapples and 

 hawthorns of the Eastern states, but. 

 singular as it may seem, it was unknown 

 until about 1910 in Europe and Asia, 

 where the pear and apple are native. 

 These facts point to the Eastern United 

 States as the native home of this disease 

 and that wild fruits of the pome family, 

 such as erabapple, hawthorn, mountain 

 ash and service berry, are its native host 

 plants. It injures these trees, however, 

 to a very much less extent than it does 

 the more sappy and vigorous growths of 

 the cultivated pear, apple, quince and 

 other fruits of the pome family. It is 

 very important that every one should 

 know that the pear and apple are not the 

 only species of tlie pome family that may 

 be destroyed by blight. In some recent 

 publications it has been noted that no 

 reference has been made to any other 

 species of the pome family than the pear 

 and apple. This is a serious mistake. 

 Orchardists should know, for instance, 

 that the quince is most seriously at- 

 tacked by this disease. The writer knows 

 an instance where an entire district be- 

 came infected through a single case of 

 blight which had its starting point in a 

 loquat. Therefore, let it be understood 



tliat the pear, apple, quince, loquat, haw, 

 service berry and mountain ash are all 

 more or less subject to this disease. To 

 a limited extent the disease also affects 

 some plums and the apricot. It has been 

 noted as attacking the blossoms and 

 young shoots of the latter varieties of 

 stone fruits. However, from a patholog- 

 ical standpoint, it cannot be considered 

 as a serious disease for any of the stone 

 fruits. 



Although the disease was known as 

 early as 1780, it was not until 1878 that 

 Professor T. J. Burrill, of the University 

 of Illinois, one of the pioneer plant path- 

 ologists, discovered the true nature of 

 this disease and named the organism 

 which causes it, namely, Bacillus amy- 

 lovorus. From the early date when pear 

 blight first became recognized as a dis- 

 ease up to the time that Professor Bur- 

 rill discovered its true cause there had 

 been much discussion regarding it, but 

 most of the discussions are of little inter- 

 est at the present date. I may also add 

 that even now there are many so-called 

 fruit growers who do not care to believe 

 the facts now so well known to every 

 worker in plant pathology. Rather than 

 believe the unquestioned facts which 

 have been made known by the micro- 

 scope, they are even willing to delude 

 themselves by such explanations as were 

 given by those who first recognized the 

 disease — such as lightning, frost, heat 

 and various other causes. Dr. Burrill's 

 discovery of the nature of pear blight is 

 of striking and fundamental importance 

 inasmuch as it was one of the first, if not 

 the first, bacterial diseases of plants to be 

 discovered. A Dutch botanist, Dr. Wakker, 

 discovered a hyacinth disease about the 

 same time to be of bacterial origin, and 

 it may be said that this is the only rival 

 in priority to Dr. Burrill's pioneer dis- 

 covery. At this time, research along the 

 lines of plant pathology, especially along 

 bacteriological lines, was not being car- 

 ried on with a great deal of vigor, and 

 even after the above-named discoveries 

 of Dr. Burrill and Dr. Wakker, a good 

 many prominent bacteriologists hesitated 

 in accepting this work with any great 



