4 H. E. Thomas and W. D. Mills 



While many species of plants 1 are affected by one or more or these 

 diseases, the number of species which have any important relation to 

 rust of apples in the Hudson Valley is apparently much smaller. 



Cedars 

 All of the three fungi are generally distributed on the red cedar 

 (Juniperus virginiana L.) in the telial stage, and two of them, G. 

 globosum and G. germinale, are perennial on the cedar. G. germinale 

 is more evenly and abundantly distributed through the cedar areas than 

 the other two species, which tend to be localized near apple or hawthorn 

 trees. G. germinale may occur also on the juniper (Juniperus com- 

 munis L.), but the juniper is not commonly associated with fruit trees 

 in eastern New York and we have not encountered it. 



Apples and related plants 

 Our observation on the aecial stages of these fungi, most of them 

 made in 1928, indicate that the following are the principal suscepts in 

 the Hudson Valley: for G. juniperi-virginianae, apple; for G. globosum, 

 hawthorn (many species) and apple; for G. germinale, quince, hawthorn, 

 and apple. We have rarely found G. globosum on pears, and in no 

 case causing severe disease on this plant. 



PREVALENCE ON VARIETIES OF APPLES, AND LOSSES 



Many lists of susceptible and resistant varieties of apples have been 

 prepared, but a considerable variation exists among these. Whether this 

 variation is due to differences in the observers, to differences in behavior 

 of the disease or diseases in different localities, or to differences in the 

 fungi which produce the diseases, cannot be stated with certainty. It 

 is clear, however, that varieties in the Hudson Valley which have until 

 recently been rated as highly resistant, are now showing approximately 

 as great an incidence of rust as are other varieties which are generally 

 regarded as highly susceptible. It is apparent also that we are dealing 

 with three distinct diseases, two of which are probably rare in many 

 localities in which observations have been made. Another cause of the 

 apparent or actual divergence of our records from those of earlier 

 workers is the fact that we have given comparatively greater attention 

 to infection of fruit than to that of foliage. 



In the herbaria of the Department of Plant Pathology at Cornell 

 University are two specimens of quince rust on apple fruit and three 

 specimens of hawthorn rust on apple foliage, all from New York State. 

 The earliest date for the quince rust is 1903, and the earliest of the 

 hawthorn-rust collections was made in 1908. 



1 Kern (1912) has assembled comprehensive lists of the species of plants known to 

 be affected by these diseases. A few additions have been made since the publication 

 of those lists. 



