252 PRODUCTIVE FARMING 



EXERCISE. Cedar Apples. In the fall or winter stu- 

 dents may find specimens of the winter form of the cedar 

 apple, above described, on the cedar trees near apple orchards. 

 If these are found use the specimens to illustrate the lesson 

 on apple disease. 



Potato Scab. On the surface of Irish potatoes in the 

 winter time may be found scabby-looking spots or areas 

 caused by the potato scab fungus. The disease when very 

 bad produces deep depressions or pits in the surface of the 



FiG. 146. Disease called "little-peach." Healthy fruit above. 

 (Experiment Station, N. J.) 



tubers. The crop yield may be greatly reduced by the 

 attacks of this disease. The spread of the disease may be in 

 several ways: 



1. The germs of potato scab will grow more rapidly 

 when there has been a heavy application of fresh stable 

 manure to the field just before the potatoes are planted. It 

 is better to manure the field one year in advance if possible, 

 or to use some well-rotted manure. 



2. When lime is applied to the soil the disease will likely 

 be worse on the potato crop. Green manure plowed under 

 in preparing the field for potatoes will help to counteract 

 this action of the lime. 



3. Soils from which a very scabby crop of potatoes has 



