502 FIELD CROPS 



with the bedding at terminal points. In the latter case, they 

 are very likely to be transported to near-by farms in manure. 

 Many weeds first appear in new localities along the railroads, 

 and then spread to adjoining fields. 



Packing material for nursery stock and other articles 

 which are brought to the farm from distant points furnishes 

 another means for the spread of weeds. Weed seeds are also 

 carried from farm to farm or from one locality to another in 

 grain and hay which are purchased for feeding. The seeds 

 pass into the manure and are then spread to the fields. 



The sowing of weed seeds with grain, grass, or clover seeds 

 is one of the most frequent methods by which the dissemi- 

 nation of these pests is effected. 



METHODS OF ERADICATION 



694. Weed Laws. Many states have adopted laws to 

 prevent the spread of weeds. Weed control laws are of two 

 forms, those which require the destruction of certain weeds 

 along roads and railroad rights of way and, in some cases, 

 in fields, and those which are aimed to control the dissemi- 

 nation of weed seeds in the seeds of grain and grasses sold by 

 dealers. The laws in the various states differ greatly in 

 their stringency and efficiency, some states being practically 

 without legal means of weed control. 



695. Annual Weeds. One of the most effective means of 

 eradicating annual weeds is to prevent them from producing 

 seeds. As they have no other means of living over from year 

 to year, annual weeds would soon be destroyed if seed pro- 

 duction were entirely prevented. This, of course, is not 

 practical, but every possible means should be used to reduce 

 the number of seeds which mature. Weeds of all kinds are 

 killed very easily when they are small by stirring the soil 

 sufficiently to expose their roots to the sun. Harrowing or 

 disking will destroy weeds soon after the seeds germinate, 

 which perhaps would survive much more severe treatment 



