32 BULLETIN 12 4 5, U. S. DEPARTMENT OF AGRICULTURE 



Thurber Loco Weed (Astragalus thurberi) 



Thurber loco weed (pi. 21) has a range similar to that of the 

 sheep loco, resembles Wooton loco weed, and sometimes is found in the 

 same places. It can be distinguished from Wooton loco weed by the 

 rather small, round pods, resembling large peas. As the pods grow 

 on long steins, they are rather conspicuous. It is thought that this 

 plant affects horses more especially, but it is known to be poisonous 

 to cattle and probably is toxic to sheep. Its toxicity is about the 

 same as that of Wooton loco weed. 



Two-Groove Loco Weed (Astragalus bisulcatus) 



Two-groove loco weed (pi. 22) is found from Alberta, Sas- 

 katchewan, and Manitoba as far as New Mexico and Oklahoma. It 

 is a tall, coarse plant with an offensive odor. The flowers are pur- 

 ple, and the pods are two grooved. This plant has been said to pro- 

 duce loco symptoms in cattle in Wyoming and also to be poisonous 

 to sheep. While there are very few experimental data, it is possible 

 that it may be added to the list of loco plants. 



SPECIES OF ASTRAGALUS POISONOUS EUT NOT TRUE LOCOES 



Three species of supposed loco plants have been shown to be poison- 

 ous to livestock, but do not produce true loco symptoms. These are 

 called poison vetches. 



Palliser Poison Vetch (Astragalus palllseri) 



Palliser poison vetch, Astragalus palliseri (pi. 23), known in 

 Canada as timber loco, extends from Canada a short distance into the 

 northwestern United States. Its stems are about 1 foot in height; its 

 flowers are purple and its pods narrow, about one-half inch long and 

 circular in section. It has been shown in Canada to be poisonous to 

 all classes of livestock, but especially so to females in milk. The 

 symptoms are not at all like those caused by locoes. No cases have 

 been reported in the United States. 



Four-wing Poison Vetch (Astragalus tetrapterus) 



Four-wing poison vetch {Astragalus tetrapterus) has been found 

 only in Utah and Nevada. There it has caused losses of cattle and 

 sheep and is suspected of poisoning horses, but none of these animals 

 show true loco symptoms. It has white or light purple flowers and 

 is readily distinguished by the pods (pi. 24) from other Astragali. 

 The pods are curved, woody, and have four pronounced wings. 



Straight-stem Poison Vetch (Astragalus sabulosus) 



Straight-stem poison vetch, A. sabulosus, sometimes known as A. 

 praelongus, is a large, smooth, erect plant found from southwestern 

 Colorado to Nevada, and south to central Arizona and New Mexico. 

 It is shown in Plate 25 and has yellowish flowers in thick clusters; the 

 pods are woody, oval, short-pointed, single-celled, and an inch long. 

 It is most readily recognized by the character of the pods. Reports 

 of poisoning by this plant have come from Magdalena, N. Mex. 





