SPRAYING TO KILL WEEDS 537 



Among the common weeds of grain fields are wild oats, 

 wild garlic, wild mustard, Frenchweed, peppergrass, smart- 

 weed, Russian thistle, knotweed, wild morning glory, corn 

 cockle, milkweed, marsh elder, ragweed, kinghead, Canada 

 thistle, and sow thistle. 



708. Spraying. The use of chemicals in destroying weeds 

 in grain fields, and to a lesser extent in meadows, pastures, 

 and lawns, has come into prominence in recent years. If 

 applied while the plants are young, the chemical spray is 

 effective in killing practically all broad-leaved plants, while 

 it does little injury to the grains and grasses. A single 

 application will kill many annual weeds and young plants 

 of the biennials and perennials, but several applications must 

 be made to kill the older perennials, as only the top growth 

 will be destroyed by the earlier sprayings. The most com- 

 mon chemical which is used is iron sulfate, at the rate of 

 100 pounds to 50 gallons of water. About 50 gallons of the 

 solution are required to spray an acre. The weeds which 

 can be successfully treated with this spray include wild 

 mustard, Frenchweed, peppergrass, shepherd's purse, rag- 

 weed, kinghead, and marsh elder. It is less effective on 

 Canada thistle, dandelion, and other more persistent weeds, 

 unless the treatment is repeated several times. Clover and 

 alfalfa are injured more or less by the use of any chemical 

 spray. 



709. Weeds in Meadows. As in grain fields, prevention 

 is more effective than after treatment in dealing with weeds 

 in meadows. The land should be in good condition when the 

 seed is sown, and the seed itself should be free from weed 

 seeds. Clipping the field in the fall after the land has been 

 seeded to grass will prevent many weeds from seeding. The 

 seeding of weeds in older meadows may often be prevented 

 by cutting the hay crop a little earlier than would otherwise 



