CROP ENEMIES AND FRIENDS 205 



As the fungi persists in the soil often as long as eight years, the 

 same crop should not be planted on that field for several years. 

 Instead, there should be planted crops, such as corn, that are not 

 subject to wilt diseases. Wilt-resistant varieties of cowpeas, 

 cotton, flax, and other plants have been bred by selection, but rota- 

 tion of crops should never be neglected, even when these varieties 

 are used. 



Preventives for Fungous Diseases. The damage of fungous 

 diseases in fields, orchards, and gardens amounts every }ear to 

 millions of dollars. Is there no way to prevent this loss? Yes, 

 there are remedies for most of these diseases, remedies both cheap 

 and. effective. The farmer should know and use them. He should 

 bear in mind the fact that most fungous diseases are contagious, 

 and that they spread by means of spores which increase very rapidly. 

 He should know and guard against the various host-plants of a 

 fungus, and should know at what season it attacks its hosts. 



How to destroy Fungi. A farmer ought to destroy the fungi in 

 and on the soil as far as possible. He can do this in two ways. 



First : He should burn diseased plants. Diseased vegetable 

 matter, such as twigs affected with blight, tobacco and cotton which 

 die from wilt, apples shriveled with bitter rot, should be collected 

 and burned. Usually this should be done on the field where they 

 are gathered, so as not to spread disease. 



Second : The fungi in the soil should be destroyed by starving 

 them. Host plants should not be grown for several years on a 

 field where they have been attacked by soil fungi, tobacco with 

 wilt, sweet potatoes with rot. 



The farmer should protect his crops against common diseases 

 by planting and by breeding resistant varieties. There are rust- 

 proof varieties of oats, and wilt-proof varieties of many plants sub- 

 ject to this disease. Our native gooseberries resist mildew better 



