FRIENDS AND ENEMIES OF PLANTS 173 



annually in the United States is estimated at S3, 000, 000. It 

 may be checked by spraying with the Bordeaux mixture before 

 the buds open. 



Wilt is a disease caused by a soil fungus which enters the plant 

 through the roots and forces its way upward into the stem, and 

 chokes the ducts or passages and shuts off the flow of the sap from 

 the roots to the leaves and branches of the plants. The water 

 supply being shut off from the leaves, they soon wilt and wither 

 away. The plants most commonly attacked by wilt are cotton, 

 flax, tobacco, and cowpeas. It may be remedied by frequent 

 crop rotations and by selecting wilt-resistant varieties of these 

 plants. 



Potato Scab. Potatoes are often covered with a rough coating 

 of scabs caused by a fungous growth which starts on the surface. 

 It may be checked by soaking the seed potatoes in a weak solution 

 of formalin, one half pint with fifteen gallons of water, for two 

 hours or more. The same solution may be used several times. 

 Treated potatoes must be planted in clean soil, that is, soil free 

 from scabby tubers from previous years. 



Potato Blight is a disease which attacks the leaves of the potato 

 and rapidly extends its ravages until it completely destroys the 

 plant. Its presence is generally heralded by the appearance of 

 brown spots upon the margin or body of the leaf. It also causes 

 a rot of tubers. The best remedy is spraying with the Bordeaux 

 mixture to which a little Paris green has been added. 



Club Root is a disease of the cauliflower, cabbage, and turnip 

 which causes an undue enlargement of the roots of each of these 

 plants. It may be prevented by a liberal addition of lime to the 

 soil. 



Black Knot is a contagious disease which attacks the branches 

 and twigs of both sour cherry trees and plum trees and brings on 

 decay and death. The most satisfactory remedy is to cut out all 

 branches affected and burn them in January before the growing 

 season commences. 



Weeds. In a general way we all have the same idea of what 

 is meant by weeds, but sometimes we find it hard to make a 

 proper distinction between them and ordinary plants. All plants 

 out of place or that persist in growing where they are not desired 



