DRIVING AND HERDING STOCK 247 



easily destroyed; and, if they are grazed so closely as to be elim- 

 inated, the desirable vegetation is also killed out. Similar results 

 may be expected where other perennial toxic species occur. 



It is known that poisonous plants generally increase in abun- 

 dance where the ranges are overgrazed. As the productivity 

 of the range is increased, many species of poisonous plants will 

 be crowded out by desirable forage species. This appears to be 

 especially true of the low larkspurs, death camas, sneezeweed, 

 and, to a lesser extent, of the locos. 



Chemical destruction of poisonous plants has been tried more 

 or less extensively but without great success, because the other 

 vegetation is killed as well. Various chemicals, such as arsenite 

 of soda, common salt, and petroleum may be used to kill poison- 

 ous vegetation, but to discover a substance which will act in a 

 selective way upon the undesirable species is difficult. 



Grubbing or frequent cutting are the most effective methods 

 thus far developed for destroying poisonous plants. The grub- 

 bing of tall larkspur is a conspicuous example of practical eradi- 

 cation. Growing as larkspur does, characteristically in some- 

 what isolated patches, the grubbing can usually be done at a cost 

 per acre of less than half the value of a two-year-old steer. Again, 

 water hemlock, which occurs commonly in patches on wet land, 

 can also be dug out economically. Less success may be expected 

 in the way of eradication by grubbing of such plants as the locos, 

 death camas, or lupine, on account of their scattered growth. 

 All species can be killed in time by cutting off the plants close 

 to the ground. Usually three or four cuttings are required for 

 complete eradication. 



Driving and Herding Stock. — It is often necessary to move 

 sheep considerable distances in changing from one range to 

 another. Some of the most serious cases of poisoning recorded 

 have occurred during these drives. If sheep are driven hastily, 

 they are hable to snatch many plants which they would not 

 devour if they were feeding at leisure. When feeding quietly 

 on the range, tne-^'^ exercise considerable choice in the selection 

 of forage; but when they have been driven steadily for a con- 

 siderable period and are quite hungry, they are apt to nip off 



