210 THE BOOK OF ALFALFA 



It is probable that the seeds thoroughly ripened will 

 retain their germinating powers for some years. The 

 purchase of hay from dodder infested fields, or the pur- 

 chase of manure from barns where infested hay has been 

 fed, are sure sources of contamination, 



"Where a newly seeded alfalfa field shows evidence of 

 (juite general dodder infection, it is useless to attempt to 

 eradicate it, and the field should be plowed up and planted 

 with some hoed crop for a period of years. Old fields 

 that have been thoroughly infested will probably be more 

 economically treated in this manner than in any other. 

 In newly sown fields, one of the most effective methods 

 is probably hoeing over the spots where the dodder 

 appears, ^going over them once in two weeks and allowing 

 nothing to grow on them until the dodder seed is ger- 

 minated. A modification of this method has been used 

 successfully by spading in fields where the colonies of 

 dodder were seen, raking out all the tops, roots and 

 branches, adding a little straw or hay and burning the 

 mass, and then keeping the spot thoroughly hoed for a 

 season. For fields where the colonies are small and scat- 

 tered, this method of hoeing and shallow cultivation is 

 probably the most practicable, as it helps to secure the 

 early germination of any seeds that were left in the 

 ground, and also kills them as soon as they are germi- 

 nated. If the seed has developed, one must be careful not 

 to spade it in too deep, as it may retain its vitality for 

 some years if left covered in the moist soil. 



'^Burning has been recommended by some, raking the 

 dodder vines and what is left of the alfalfa to the center 

 of the colonies, putting brush or straw with it, together 



