322 PROCEEDINGS OP THE ACADEMY Of [1886. 



HISTORY AND BIOLOGY OF PEAR BLIGHT. 

 BY J. C. ARTHUR. 



To the American orchardist or nurserj'man the name of pear 

 blight, or fire blight, as it is often called, brings to mind a serious 

 malady of fruit trees, which has been the theme of incessant dis- 

 cussion by horticultural writers and speakers since the earliest 

 days of fruit culture in this country. The most marked featui'es 

 of the disease were admirably characterized bj^ William Coxe^ at 

 the beginning of the present century, in the following words : 

 " That species of blight which is sometimes called the fire blight, 

 frequently destroys trees in the fullest apparent vigor and health, 

 in a few hours, turning the leaves suddenly brown, as if they had 

 passed through a hot flame, and causing a morbid matter to exude 

 from the pores of the bark, of a black ferruginous appearance ; 

 this happens through the whole course of the warm season, more 

 frequently in weather both hot and moist." The disease occurs 

 from Canada and Minnesota on the north, to Georgia and Louis- 

 iana on the south, and from the eastern limit of the Rockj- 

 Mountains to the Atlantic ocean. No part of this vast extent of 

 country is exempt, although it does not appear with the same 

 frequency and power in all localities, and is usually rai^e in the 

 immediate vicinity of the sea-coast. 



So far as at present known, it is exclusively confined to this 

 part of North America. This is partly inferred from the absence 

 of any distinct mention of such a disease in the horticultural 

 literature of other regions, and partl^^ from direct testimony. 

 Prof. Dwindle, late of the University of California, has told the 

 writer that it does not occur on the Pacific coast. Dr. De Bary,^ 

 whose word carries great weight, says, after giving a brief 

 description of the disease, "this phenomenon is not to my knowl- 

 edge known in Europe." A long account of the disease has been 

 published by Dr. Wakker,^ in a gardening journal of Holland, in 

 order to learn if it occurs in that country, but up to the present 



1 Cultivation of Fruit Trees, Philadelphia, 1817, p. 174. 



^ Vorlesungen liber Bacterien, 1885, p. 137. 



3 Nederlandsche Tuinbouwblad, II (Jan. 9, 1886), p. 9. 



