Weeds and Their Control 377 



portant. Mowing pastures and fencerows or pasturing off the 

 weeds with sheep and cattle are efficient means of destroying 

 weeds if practiced before they come into bloom. 



Preventing the introduction of weed seeds. Weed seeds are 

 introduced not only by the purchase and planting of uncleaned 

 seeds but through other common practices. The use of fresh 

 manure is a common source of weed introduction. Stock feeds 

 made from screenings are likely to contain a large percentage of 

 weed seeds. Finally, the seeds that may be spread by the wind 

 from neighboring lawns and farms make the problem of weed 

 control a community affair. One careless neighbor is a menace 

 to the entire community, and he should be treated as we treat 

 any one who maintains a nuisance. Cooperation through com- 

 munity organizations is essential to efficient weed control. 



Poisonous weeds. Not only may weeds reduce crop yields, 

 but some weeds are poisonous to human beings and to animals. 

 Poison ivy is poisonous to many persons who come in contact 

 with it. White snakeroot produces " trembles " in cattle and 

 " milk sickness " among human beings who use milk from such 

 cattle. Wild cherry leaves, especially when in a wilted con- 

 dition, are poisonous to cattle. Larkspur and loco weed are 

 poisonous to cattle and a great source of loss in Western pastures. 

 Wild onions, garlic, and other less-well-known aromatic herbs 

 produce unpleasant odors and tastes in dairy products. All 

 these plants can be destroyed by persistent and intelligent effort, 

 and the results are of such far-reaching importance that their 

 eradication will in the end be profitable. 



