DISEASES 217 



Cedar rust on the fruit appears as bright-yellow spots. It occurs 

 in the majority of cases in and around the blossom-end depression. 

 Spores are produced from the diseased areas in projections like 

 those occurring on the leaf. The fungus penetrates into the flesh 

 of the apple, producing a yellowish, atrophied condition of the cells. 



It is well known that certain varieties of apples are more resist- 

 ant to the disease than others. In some varieties it is the foliage 

 that is most affected, while in others it is the fruit. The foliage 

 of the Ben Davis and the Shockley is extremely susceptible to this 

 rust, while the fruit of the latter suffers almost as much as the foli- 

 age. The principal injury wrought by the disease is to the foliage, 

 for this naturally reacts on the whole tree. The diseased leaves fall ; 

 in some instances nearly complete defoliation takes place, with 

 the result that the feeding functions of the whole organism are 

 impaired, to the detriment of the crop on the trees and of the fruit 

 buds of the succeeding crop. 



Treatment. The surest method of preventing the establishment 

 of cedar-rust infections in orchards is to remove all cedar trees and 

 shrubs within a radius of at least a mile. The source of infection is 

 always the cedar, since the fungus cannot exist without reproducing 

 itself in this tree at one time in its history. 



W. W. Chase 1 says that he has had only indifferent success in 

 spraying against the disease. The sprayings were beneficial, but 

 far from satisfactory. A fourteen-year-old Shockley orchard was 

 used in the experiments, portions being sprayed with atomic sul- 

 phur and others with prepared lime-sulphur. The disease gets its 

 start in early spring, at a time when wet weather favors the pro- 

 duction of the spores on the cedar balls and their germination on 

 apple trees. To be most beneficial the treatment should begin 

 with the appearance of the foliage and continue at intervals of 

 from ten days to two weeks, until the leaves and fruit are well 

 covered by a protective fungicide. 



Apple scab (Venturia pomi [Fr.] Wint.). With the single excep- 

 tion of abnormally virulent outbreaks of bitter rot, no disease of 

 the apple is of more economic significance than apple scab. In 

 orchards where no measures are taken to prevent or control it, the 

 scab-diseased fruit may easily outnumber the scab-free fruit two to 



1 Assistant state entomologist, Georgia. 



