Three Rust Diseases of the Apple 5 



Only one published account has been found to indicate that hawthorn 

 rust occurs commonly on cultivated apples. Thaxter (1891), working in 

 Connecticut, states "that perhaps the most common orange rust of apples 

 in this State is undoubtedly caused by this species [G. glob o sum]. " 

 Professor Thaxter recently stated (in a letter dated November 9, 1928) 

 that G. globosum on apple seems to be commoner farther south in New 

 England than it is in southern Maine, where it very seldom occurs on 

 cultivated apples but is not uncommon on wild stock. Dr. F. D. Kern 

 also states (in a letter dated October 10, 1928) that G. globosum is not 

 uncommon on apple foliage in the New England States. He has obtained 

 collections from Connecticut, Maine, Massachusetts, New York, and Ver- 

 mont. The only printed account which we have found of quince rust 

 as an important disease of the apple, is presented in two brief notes 

 from Nova Scotia by Hockey (1926, 1927). Dr. W. G. Farlow reported, 

 in conversation with Dr. F. D. Kern a number of years ago, that G. 

 germinate was not uncommon on apple fruits in the vicinity of Boston 

 (letter from Kern dated October 10, 1928). Unfortunately, no more 

 detail seems to have been preserved. Mr. Hockey has kindly submitted 

 the following notes in a letter of October 18, 1928 : 



Previous to 1924, apple rust was reported from Nova Scotia as caused by 

 Gym oosporangium juniperi-virginianae Schw. A very careful survey in subsequent 

 seasons has established that this disease is caused by G. germinale ( Schw. ) Kern. 

 The alternate host for this rust is Juniperus communis var. canadensis Loud., a 

 very prevalent plant in waste pastures and rockj' slopes in the Annapolis Valley. 



The Roestelia stage was identified on Amelanchier, Crataegus, Cydonia spp., and 

 on Gravenstein apple. It has been observed fruiting on Bishop Pippins, but no 

 specimens have been examined by the writer. The disease is commonly observed at 

 the calyx end of the fruit, causing a dark green, seminecrotic area. Very few fruit 

 infections produce aecia, and infections on apple foliage have not been positively 

 identified. Rust has been observed on the following varieties of apples : Crimson 

 Beauty, Yellow Transparent, Gravenstein, Mcintosh, Fameuse, Ribston Pippin, 

 Bishop Pippin, Wagener, Tompkins King, Stark, Baldwin, and Russet. 



Another species of rust found on the low bush juniper, locally, is G. claveriaeforme 

 (Jacq. ) D. C. Aecia of this species have been found on Amelanchier and Crataegus 

 spp. but not on apple. 



The red cedar, Juniperus virginiana L., is to be found in very scattered areas in 

 Nova Scotia, and no rust resembling a Gymnosporangium species has been reported 

 on this host. 



Specimens of Gravenstein apple fruits bearing pycnia of G. germinale 

 have been received from Mr. Hockey. 



Tn view of the lack of knowledge of the hawthorn and quince rusts on 

 apples, records of fruit and foliage infection are given here in some 

 detail. No records of actual percentage of infected fruit were made by 

 the writers in 1927. However, it was estimated that up to 50 per cent 

 of Mcintosh fruit was infected in some orchards. A. S. Mills 2 reports 



- Typewritten report of special field assistant. Departments of Plant Pathology and 

 Entomology, Cornell University. 



