268 



Diseases of Economic Plants 



suggested for the prevention of these pests: placing laurel 

 branches in the field, change of seed, avoidance of manures, 

 thorough screening, soaking in brine, etc. 



Fig. 145. — Oat plants, smutted and healthy; note 

 difference in height. 



Preventive treatments, — One early remedy that has 

 proved its value and remained in common use, soaking the 

 seed in copper sulfate, was first tried l)>' Tessier in 1789, after 

 he, in 1786, and Young, in 1787, had tested numerous chem- 



