324 PROCEEDINGS OP THE ACADEMY OP [1886. 



destroys trees in the fullest apparent vigor and health, in a few 

 hours ; I have in twenty years lost upwards of fifty trees." The 

 years 1826 and 1832 were notable in horticultural circles for the 

 increased prevalence of the disease; but it was in 1844 that the 

 most widespread and fatal epidemic, that the country has yet 

 known, occurred. Few, if any, pear-orchards escaped at that 

 time without the pai'tial or total loss of many trees, and some 

 orchards, even large ones, were quite destroj-ed. The following 

 year the epidemic was much lighter, and had fully disappeared 

 by 1846. Although it had subsided as an epidemic, it still 

 occurred in localities here and there, and has continued to do so 

 until the present time. Judging from the communications in the 

 horticultural press, the whole country, or various sections of it 

 independently, have been subject at various times to epidemic 

 visitations, but none have equaled in severity that of the memor- 

 able year of 1844. 



It is often maintained that a certain periodicitj' of occurrence 

 is observable, the periods usually being placed at five, ten, or 

 twenty years. A careful examination of the literature of the 

 subject, however, gives little support to these views, and makes 

 it more probable that the intervals are irregular, and that they 

 vary for different sections of the country. The year of maximum 

 prevalence may or may not be preceded by one in which the 

 disease is noticeably common, but it is quite invariably followed 

 by a year or two of successive decadence. 



In the absence of exact statistics, which it has not been prac- 

 ticable to obtain, something of the important nature of the disease 

 may be gathered from the statements of horticultural writers and 

 the phraseology which they employ in speaking of it. 



The renowned horticulturist, A. J. Downing,' called it the 

 "monstrous malady of the pear." Chas. R. Baker ^ saj^s it is 

 " the worst malady with which the cultivator of the pear-tree has 

 to contend." In southern Pennsylvania "the'pear is so generally 

 destroyed by the blight," according to J. B. Garber^ writing in 

 1850, "that very few trees are to be found." At Philadelphia, 

 however, the disease has been rarely observed, according to 



1 Horticulturist, vol. i, 1846, p. 62. 



' Practical and scientific Fruit Culture. Boston, 1866, p. 476. 



U. S. Patent Office Report for 1850, pt. ii, p. 418. 



