Although the damage done by quince rust is not of great extent, nevertheless the disease has a general prevalence in the region from New England west to northern Michigan, and south to Florida. Outbreaks have been known in Massachusetts in 1897, in western New York in 1910, and the trouble is commonly observed in Alabama, South Carolina, North Carolina, New York, Pennsylvania, New Jersey and Iowa. Generally speaking, quince rust is not common in the Mississippi Valley. Affected fruits are usually worthless and rusted twigs are considerably malformed.
Diseased fruits (Fig. 114) are very conspicuous in July and August. The injured portion is covered wholly or in part by masses of orange fringe-like growths, the whole presenting a yellow woolly appearance (Fig. 114). Some fruits are attacked at the stem end, others at the calyx - end. Again the whole fruit is involved and it may fall. More often, however, it hangs to the tree, dies, and becomes black and hard. There is usually considerable distortion.
Fig. 114. - Quince rust.
Fig. 115. Rust on quince - twig.
Twig-infections (Fig. 115) are commonly found at the base of new shoots, and knots are produced which resemble Black Knot of plums.
The quince rust fungus, Gymnosporangium clavipes, has a peculiar life-history. A part of its cycle is spent on the quince and related plants like the juneberry, hawthorn and apple. But in order to complete the life-history it must have the red cedar, or juniper (Juniperus communis and J. vrginiana). On the red cedar twigs there are produced peculiar canker-like lesions (Fig. 116). These diseased spots begin their development in midsummer. The fungus hibernates within the twig as mycelium. With the advent of the first warm, moist spring weather the fungus resumes growth and development. On the surface of the affected area numerous yellow, gelatinous masses appear, - the teliospores of the fungus. Each teliospore germinates by developing a short tube (promycelium) on which four sporidia are borne. These sporidia are discharged in thousands, carried by the wind, and some of them infect the quince or the related plants already listed. The sporidia never reinfect the cedars. On the quince, the sporidia germinate, forming germtubes which grow into the tissues of the fruit and twig, causing the distortions and malformations already described. Finally the tubular projections, which in mass are an orange fringe-like growth, develop another sort of spores, - secio-spores. These are peculiar, like the sporidia developed on the cedar, in that they cannot reinfect the quince, but may infect the cedars. About one year is required for the completion of the life - history of this pathogene.
Fig. 116. - Quince rust on red cedar.
The vulnerable point of attack lies in the inability of the fungus to reinfect the quince. It must pass to the cedar. The most direct method of control is to exterminate cedars near the orchard. The juneberry and hawthorn are to be regarded as weeds in the sense that they harbor the undesirable pest, and should therefore be removed. Spraying quinces for the control of rust is not a reliable method of treatment.
Stone, G. E., and Smith, R. E. The quince rust. Massachusetts Agr. Exp. Sta. Rept. 10: 61 - 63. 1898. Stewart, F. C. Notes on New York plant diseases, I. Quince. Rust, Gymnosporangium clavipes C. and P. New York (Geneva) Agr.
Exp. Sta. Bul. 328: 385. 1910. Bailey, L. H. The quince in western New York. Rust. Cornell Univ. Agr. Exp. Sta. Bul. 80: 625-627. 1894. Halsted, B. D. Some fungous diseases of the quince fruit. The quince rust. New Jersey Agr. Exp. Sta. Bul. 91: 3 - 5. 1892. Halsted, B. D. The quince rust. New Jersey Agr. Exp. Sta. Rept.
1892: 307 - 310. 1893. Paddock, W. Plant diseases of 1901. Quince rust. Colorado Agr.
Exp. Sta. Bul. 69: 18-20. 1902. Sturgis, W. C. Miscellaneous notes on fungi. Quince rust (Rcestelia aurantiaca Pk.). Connecticut Agr. Exp. Sta. Rept. 18: 137 - 138.1895.