XII. FIRE-BLIGHT OF APPLE, PEAR, QUINCE, ETC. 



(Called also pear blight, apple blight, quince blight, etc.) 



Type. Fire-blight, so called since the time of Wm. Coxe 

 (1817), is a time-limited, rapid, parenchymatic decay, chiefly of 

 the pear, the apple, quince, and other pome fruits (Figs. 276, 277, 

 278). From stone fruits it was first described in 1902 by L. R. 

 Jones who found it on the cultivated plum (Prunus sps.). It 

 was also found independently on the plum by Merton B. Waite. 

 It has been seen on the loquat (Eriobotrya), and on the cherry. 

 It occurs also on certain wild genera, e.g., Crataegus, Amelanchier, 

 Heteromeles (Waite). O'Gara has reported it from the apricot 

 in the Northwest. Heald also has reported finding it on the 

 apricot in Texas. In 1915 the writer cross-inoculated it to 

 apricot readily. He also saw it escape naturally from inoculated 

 pears to a neighboring apricot (Fig. 279) and with the organism 

 plated from a dying apricot twig produced typical blight on 

 pear shoots. Munn has recently reported it as inoculable into 

 the blossoms of the strawberry (Phytopathology, vol. 8, p. 33). 

 Can you find it occurring naturally on the strawberry? Search 

 in the vicinity of blighting pear and apple orchaids. 



It begins by destroying the blossoms, green fruits, and young 

 shoots, including young leaves which are specially favorable 

 places for its development (Fig. 280), but it passes quickly 

 downward, chiefly by way of the bark parenchyma, into the 

 inner bark of the larger branches and of the trunk, which often 

 are girdled and killed. It gets its common name from the con- 

 spicuous black or brown appearance of the blighted branches, 

 the dead persistent leaves of which look as if scorched (Fig. 278). 

 The blackening of the leaves is a host reaction and occurs in the 

 absence of the bacteria, but the bacteria often attack leaves 

 as well as stems, passing from the stem through the petiole into 

 the leaf blade (Figs. 280, 281). As the fruits ripen and as the 

 inner (living) bark of the shoots becomes firm, in late summer or 



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