8 BULLETIN 800, U. S. DEPARTMENT OF AGRICULTURE. 



Many areas in southern Utah are given np to corn raising by dry- 

 land farming and afford another poison-milkweed problem. Some of 

 the fields are in the natural habitat of the milkweed ; cultivated soil 

 forms a better seed bed than the undisturbed soil ; cultivation breaks 

 up the horizontal roots and propagates new plants rapidly. Areas 

 of this type may be seen between Kanarraville and New Harmony, 

 Utah. 



On some of the overgrazed ranges whorled milkweed has become 

 a menace to stock. The range country in Long Valley on the Virgin 

 Elver near Mount Carmel, Utah, appears, to be an overgrazed range 

 of that sort. Arizona and New Mexico also have the same range 

 trouble. 



PART II.— EXPERIMENTAL WORK. 



Although both cattle and horses are killed by the milkweed, the 

 greater part of the experimental feeding work was done with sheep, 

 since most of the heavy losses are of sheep, and, moreover, it did 

 not seem wise to kill cattle and horses unless it was distinctly neces- 

 sary. Enough was done with cattle and horses to demonstrate the 

 toxicity of the plant for those animals and to show that the results 

 obtained from the sheep experiments could be applied to other ani- 

 mals. Table 1 gives a summary of the experiments. 



