This disease occurs also on the pear, to a discussion of which the reader is referred for additional facts and data (page 347). On the quince the Leaf Blight disease is also called Black Spot, Fruit Spot and scald. It was reported from France in 1815, and has a long history in America, now being found in practically all nursery and orchard districts in the Appalachian region. The disease is probably ever present on the quince, although it does not necessarily bring about serious difficulty. Yet in nurseries defoliation is common, and sometimes twigs are girdled. The quince orchards in New York State suffer rather severely, especially those in sod or those which are otherwise neglected. Even well - managed orchards are not always free from the disease. All varieties are susceptible.
Like the spots on pear leaves, there is produced a more or less circular discoloration on the upper surface, with a reddish center and dull borders (Fig. 113). Finally the lesion extends through the leaf-tissue showing on the lower surface. The spot on the upper surface becomes dark-brown and a characteristic blackish elevation appears in the center, - the fruiting pustule of the pathogene (Fig. 113). When the spots are numerous, they coalesce (Fig. 113); in cases of severe attack the leaves turn yellow and fall. This defoliation is common in August and September. As a result of a serious infection the quince fruits remain small and the next year's crop suffers. The lesions on the twigs are similar in appearance to those on the foliage, with the difference that twig-lesions on quince are more elongated in form and have a depressed surface. The center of the spot shows the fruiting pustule as described for the leaves. On the fruit a black spot is produced. In milder cases the spots are scattered and the effects are not serious; in more intensive attacks the fruits become cracked and lop-sided. The cause of the disease, as in the case of pear Leaf Blight, is the fungus Fabroea maculata. For its control see discussion under Pear, page 349.
Fig. 113. - Types of lesions on quince-leaves produced by the Leaf Blight fungus.
Stewart, V. B. Some important leaf diseases of nursery stock. Cornell Univ. Agr. Exp. Sta. Bul. 358: 171 - 224. 1915.
Bailey, L. H. The quince in western New York. Leaf Blight and Fruit Spot. Cornell Univ. Agr. Exp. Sta. Bul. 80: 619 - 625. 1894.
Halsted, B. D. Some fungous diseases of the quince. The quince fruit spot. New Jersey Agr. Exp. Sta. Bul. 91: 6 - 8. 1892.
Arthur, J. C. Spotting of quince fruit. New York (Geneva) Agr. Exp. Rept. 4: 275 - 276. 1886.
Thaxter, R. Leaf Spot of quince. Connecticut Agr. Exp. Sta. Rept. 1890: 99 - 100. 1891.
See additional references under Pear, page 350.