RANGE IMPROVEMENT. 319 



the sheep, when it is necessary to trail them through a patch of lupine, are 

 drifted rather than driven, and that they are well fed when they come upon 

 this locality. It seems probable that intelligent handling of bands of sheep 

 may reduce to almost nothing the losses occasioned by Zygadenus and lupine. 

 If, however, hungry sheep come in contact with fields of Zygadenus in the 

 spring or with fields of lupine in the late summer and fall, at a time when the 

 plants are bearing pods, fatal results must be expected. " 



Poisonous plants can be eradicated or kept down to a point where they are 

 not dangerous in various ways. The most thorough and likewise the most 

 expensive is that of grubbing out the roots. At the Utah Experiment Station 

 of the Forest Service, Sampson has found that cutting or mowing two or three 

 times during the first growing season and once or twice the second prevents 

 storage in the rootstocks and leads to the dying-out of the plants. Where 

 the ground is not too uneven or covered with brush, it is much cheaper than 

 grubbing, and nearly as efficacious. Sheep have also been used to graze off 

 larkspur on cattle ranges, and it appears probable that overplanting with 

 vigorous innocuous species during favorable seasons would largely eliminate 

 poisonous plants as a result of competition. 



Aldous (1917:22) has summarized the results of the methods of grubbing 

 out and grazing off larkspur on the national forests: 



"Grubbing out the plants is the most feasible method of preventing loss 

 of cattle from tall larkspur poisoning. The first grubbing costs from S3. 65 

 to $10.10 per acre, the cost depending upon (1) the number of plants per acre, 

 (2) the texture of the soil, and (3) whether or not the plants are growing in the 

 open or in willows or other brush. The cost of the second grubbing should 

 not exceed $1 per acre. Extensive eradication on four forests has been done 

 at a cost of less than one-half the value of the cattle saved annually. An 

 average of 93 per cent of the plants in the experimental work and of from 80 

 to 95 per cent in extensive work were killed by the first grubbing. By a 

 regrubbing of the area one year after the first grubbing practically all of the 

 larkspur plants were killed. 



"The use of sheep to graze off larkspur-infested cattle range has a limited 

 application. Its success depends (1) on the palatability of the larkspur, (2) 

 the availability of sheep to graze the infested area at the proper time, and (3) 

 whether the infested areas furnish sufficient forage to justify trailing sheep to 

 them." 



On the lower ranges, especially those of the grassland climax, overgrazing 

 is either a direct or a contributing cause of stock poisoning. This is naturally 

 the consequence of the disappearance of the more palatable species and the 

 correspondingly greater abundance and attractiveness of the poisonous weeds. 

 Since the evil effects of overgrazing are most in evidence during the dry phase 

 of the climatic cycle, methods of control and eradication should be focussed 

 especially upon drought periods. For example, the grubbing out of plains 

 larkspur or loco would be a simpler matter at the end of a drought period, and 

 the grasses would be enabled to develop a much more effective competition 

 during the ensuing wet period. 



Eradication of weeds and cacti. — It has been repeatedly shown that annual 

 herbs are replaced in the course of succession by perennial ones, and these to a 

 large degree by grasses. The weedy nature of the annuals is evident, but 

 perennials are often also to be regarded as weeds in a grass range, especially 



