CEREAL PESTS WEEDS 465 



the cultivator and hand hoe must be used often. After 

 it is impossible to longer use the cultivator, the use of the 

 hand hoe should continue until the crop is removed and 

 even afterward. It is of course understood that care 

 has been taken previously to prevent the production of 

 seed. 



Another method of combating the weed is by smother- 

 ing it with a vigorous thick standing crop such as rape. 

 As in the other method, the ground should be cultivated 

 until time for seeding, which for rape is in May or June. 

 Seeding of rape at 2 pounds an acre in drills, or 3 pounds 

 broadcast, is about right. When the crop attains rank 

 growth, it may be pastured or removed and fed to stock. 

 If the land is lacking in organic matter, the crop may be 

 plowed under. 



In the southwestern plains another species, blue top or 

 blue nettle (S. el&agnifolium, Cav.), also perennial, becomes 

 more common than the horse nettle. It is 15 inches high ; 

 stems and leaves ashy with scattered prickles; stems 

 little branched ; leaves wavy-margined ; flowers usually 

 purple ; fruit the size of cherries, often turning dark 

 colored late in the season ; occurs in sandy loams. Still 

 a third perennial species, bad in the Southwest, is Torrey's 

 night-shade (S. Torreyi, Gray). This species has much 

 larger fruit than the others, often reaching 1 inch in 

 diameter, and remains yellow. 



508. Perennial ragweed (Ambrosia psilostachya, DC.) 

 was reported by many farmers some years ago to be the 

 worst weed in Oklahoma. It is the most common rag- 

 weed in the western parts of other states of the Plains. 

 It differs from the ordinary ragweed of the North and East 

 (485) in having a perennial habit, thicker leaves, and a 

 nearly smooth fruit. 

 2 H 



