FIRE-BLIGHT OF APPLE, PEAR, ETC.: ERADICATION 387 



"1. Pyrus ussuriensis is more resistant to pear blight than any other known 

 species of Pyrus. 2. Many forms of Pyrus ussuriensis have so far proved immune 

 to pear blight, failing to blight, even in the tips of the young, tender, vigorous 

 shoots, when inoculated. 3. Some forms of Pyrus ussuriensis blight only in the 

 young tender shoots when inoculated, the blight usually killing such shoots back 

 only from one to ten inches, and very rarely as much as fifteen inches, in case of 

 extremely vigorous trees. In such cases the disease is usually confined to the cur- 

 rent season's growth, although very rarely and in the most extreme cases it slight ly 

 enters the previous season's wood. The disease in these forms has always been 

 confined to that portion of the branch less than one-half inch in diameter, and very 

 seldom has progressed into wood more than one-fourth inch in diameter. 



"These results were obtained in a region where pear blight is extremely viru- 

 lent, on very fertile, irrigated and thoroughly cultivated soil, which produces a 

 very vigorous growth, and where every effort has been made to induce the trees 

 to blight. Up to the present time no natural infections have ever been found on 

 the young trees of Pyrus ussuriensis." 



LITERATURE 



For literature, consult various writings of Burrill, Arthur, 

 Waite, Whetzel, L. R. Jones, D. H. Jones (Bull. 176, Ont. Ag. 

 Col.), Stewart (V. B.), Sackett, Bachmann, Fulton, Heald, 

 O'Gara, Merrill, Reimer, Stevens, etc. 



See also "Bacteria in Relation to Plant Diseases," Vol. I 

 (1905), plates 28-31, and Fig. 61. For various brief notes on 

 the organism see also the index to Ibid., Vols. I, II, III. 



The student should learn early how to use literature and 

 should be a wide and eager reader not only of all the newer 

 things but also of old books and papers. Search out all the 

 pear-blight papers from, the above hints and make a respectable, 

 chronological bibliography. 



Aderhold's note is in Aderhold and Ruhland's paper on 

 "Die Bakterienbrand der Kirschbaume," Arb. a. d. Kaiserl. 

 Bio. Anstalt f. Land. u. Forstw., V Bd., 6 Heft, pp. 334-336. 



Reimer's paper "A new disinfectant for pear blight" is 

 in Monthly Bulletin of the [California] State Commission of Horti- 

 culture, Vol. VII, No. 10, Sacramento, Oct., 1918, pp. 562-565. 



P. J. O'Gara's paper "Pear Blight and Its Control upon the 

 Pacific Coast' was published in the Medford Mail Tribune, 

 Medford, Oregon, 1910, and a separate was issued, 8 vo., pp. 1-34. 



A pear grower's observations on the disease as it occurred 

 in New Jersey in the first years of the 19th century may be found 

 in Wm. Coxe's book. Who was Coxe? 



