CEREAL PESTS t WEEDS 445 



rotation, it can be eradicated from cereals. It is quickly 

 killed by spraying with iron sulfate. 



483. Tumbling mustard (Sisymbrium altissimum, Linn.) 

 is a bad weed in grain fields, and called the worst weed in 

 Canada. The young plants form a rosette of soft, pale 

 downy leaves, deeply incised. On older plants the 

 lower leaves are runcinate-pinnatifid, irregularly toothed, 

 or wavy-margined. Upper leaves smaller, thread-like. 

 Flowers in racemes, cream-colored, pods long, slender. 

 The seeds are -^ inch long and half as thick, reddish yellow 

 in color, oblong, with 1 or 2 delicate grooves or scars usually 

 present (Fig. 142 k). > 



This is one of the tumble weeds, and in the fall, after 

 the seeds have matured, it breaks from the ground and is 

 carried long distances by the wind. It is said that a 

 single plant may produce 1,500,000 seeds. 



Tumbling mustard is rather persistent, but can be 

 controlled by thorough cultivation. Fall disking imme- 

 diately after harvest is a good practice where this weed is 

 bad. 



484. Chess or cheat (Bromus secalinus, Linn.) is a well- 

 known winter annual, common everywhere, frequent in 

 wheat fields, but occurring in fields of other winter cereals, 

 particularly winter barley. The seeds are a common im- 

 purity in winter wheat, and to a less extent in winter rye. 

 Chess is not a specially strong weed and is easily controlled, 

 as indicated by the usual manner of its appearance. It 

 usually occurs in spots in the place of winter grain that 

 has been killed from some other cause, such as the winter 

 or Hessian fly. The chess, after passing the winter, fol- 

 lowing its winter annual habit grows up quickly in the 

 bare spots in the spring, but is unable to compete with the 

 crop, where the latter is not injured in other ways. An 



