CHAPTER XIII 
QUINCE DISEASES 
THE quince is almost always attended by one or two prom- 
inent diseases, such as fire-blight and leaf-blight. These two 
troubles are perhaps the only ones in the United States which 
should arouse anxiety. Both diseases may be successfully 
combated. Rust, fruit-rots and crown-gall may also affect 
the quince. 
Fire-Biicut 
Caused by Bacillus amylovorus (Burr.) Trev. 
Fire-blight on the quince (Fig. 112) is no less prevalent than leaf- 
blight, and it is probable that the former ranks as the most im- 
portant of quince diseases. It affects orchard trees commonly, 
and in the nursery is regarded as a very troublesome disease. 
Entire blocks of quinces in the nursery have been destroyed 
by fire-blight. The twigs are killed back and on two- and three- 
year-old stock the blossoms, which occur profusely, are blighted. 
The disease occurs widely in the United States on the pear, 
quince and apple, and not infrequently is found affecting the 
hawthorn, apricot, plum, service-berry and mountain-ash. In 
the orchard the quince ranks below the pear and apple in sus- 
ceptibility ; however, in the nursery the order of susceptibility 
is as follows: quince, apple and pear. Among the quinces 
there are no marked differences in varietal resistance; all 
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