PLANTS FROM AN ECONOMIC STANDPOINT 343 



the parasite passed part of its life on barberry bushes and 

 then transferred its place of living to the wheat plant. 

 It appears on the wheat leaves and stalks as a collection 

 of reddish brown spots. It extracts its food from the 

 leaves of the wheat plant, which is so weakened that no 

 grain is produced. Since the spores germinate readily 

 only on the bar- 

 berry, the remedy 

 seems to be to de- 

 stroy the barberry. 

 Rotation of crops 

 aids in controlling 

 this disease. 



Brown Rot. - 

 A common fungous 

 disease is the 

 brown rot, which 

 attacks stone 

 fruits, particularly 

 plums and peaches. 

 It attacks the fruit 

 on the tree, its 

 appearance being 

 marked by a.brown 

 spot. The rotted 

 fruit falls to the 

 ground, or shrivels 

 and clings persis- 

 tently to the tree to form mummies that carry the disease 

 over the winter. In the spring the spores which develop 

 in countless numbers in these mummies are carried by 

 the wind to the tree blossoms, where they begin their 

 work again. The disease may be partially controlled by 



U. S. Dept. of Agriculture. 

 FIG. 305. Motor Truck Sprayer in Operation. 



