224 THE CHIEF SOUTHERN AGRICULTURAL CROPS 



scale, though they are less susceptible than the 

 peach, pear, or plum. They are also often infested 

 by another scale, the oyster-shell bark louse. The 

 same line of treatment suggested for the San Jose 

 scale on peaches will be effective for any of the scales 

 found on apples. 



The apple leaf rust (G-ymno sporangium) is an- 

 other disease that should be mentioned. It is a 

 fungous disease causing conspicuous yellow spots on 

 the leaves. On the under side of these spots clusters 

 of minute horn-shaped receptacles appear that are 

 filled with spores. This disease is a peculiar and 

 interesting one, since the fungus which causes it 

 passes through two very distinct stages. The spores 

 formed on the apple leaves will not grow again on 

 the aj^ple, but if blown to a red cedar they quickly 

 germinate and form small galls on the twigs, which 

 the following spring develop into the unsightly 

 orange-colored masses, usually known as " cedar ap- 

 ples," that are such familiar objects wherever apples 

 and red cedars occur in the same neighborhood. It is 

 the spores produced on these '^ cedar apples " that 

 again infest the young apple leaves and cause the 

 yellow rust spots. Cutting down all the cedar trees 

 in the neighborhood of an apple orchard is the surest 

 remedy for this trouble. Spraying with Bordeaux 

 mixture at the time that the "cedar apples" are 

 maturing spores will also give some protection. 

 Many varieties of apples show a marked immunity 

 from this disease. Red Astrakhan, Winesap, and 

 Ben Davis are seldom or never attacked by it, while 

 Red June, Jonathan, and many other varieties are 



