1909.] 



" Couch " or " Twitch." 



281 



Black twitch, of which there are several slightly dif- 

 ferent varieties, is as troublesome as couch, and is propagated 

 in the same way, namely, by seeds and by its creeping stems. 



Onion " Conch." — This is a peculiar variety of tall oat- 

 grass met with locally, perhaps more particularly on the 

 lighter class of soils. Where it has once got possession of 

 the land it is practically impossible to get rid of it entirely. 

 The characteristic features of this pest are the swollen inter- 

 nodes found at the base of the stems just below the surface 

 of the soil. Each "onion" is solid, smooth, and round, 

 about the size of a large pea, and is capable of withstanding 



/ 



FIG. 4. —ONION COUCH. 



drought for a long time. Several are joined together, and 

 resemble, a short string of beads (Fig. 4). They are easily 

 detached from each other by harrows and other implements, 

 and as each little knob possesses a bud the pest readily spreads 

 over the land. The inflorescence of the plant is a large 

 panicle, the branches of which are somewhat closely pressed 

 to the main stem both before and after flowering. The spike- 

 lets and "seeds" are as large as those of a small oat, and 

 resemble them in form ; the flowering glume has a bent 

 twisted beard or awn attached to it. 



Remedies. — 1. As all these pests are spread by means of 

 their seeds, which are easily blown about, every effort should 



x 



