10 CIRCULAR, ee, U. S. DEPARTMENT of agriculture 



of plants is to destroy all the infected individuals, preferably by 

 burning them. Many 'suggested remedies for this disease have been 

 applied, but without success. 



insect pests 



The Bureau of Entomology of this department has investigated 

 cactus insects extensively. The results of this work appear in a 

 bulletin (8). 



Cactus fanciers in the Southwest, particularly in California, should 

 be careful not to introduce the native cottony cochineal (Dactylopius 

 tomentosus) into their plantings. This insect is particularly injuri- 

 ous when introduced without its parasites, which has been done in at 

 least one notable instance in California. When this insect is brought 

 into a planting it multiplies rapidly during the long. hot. dry sum- 

 mers and is very destructive to a large number of species of prickly 

 pears. It does not attack them all. however. 



In the plantation on the United States Plant Introduction Garden 

 at Chico. Calif., it was introduced on Xew Mexican species of 

 Opuntia and spread rapidly to species from Texas and Arizona, 

 and also certain ones from Mexico. It has not attacked the cylin- 

 drical species, the spineless forms of the Indian-fig group, the 

 mansa forms (large cultivated Mexican species), or the large tree 

 forms generally, with the exception of Opuntia monacantha. of 

 South American origin, which proved to be particularly susceptible. 

 This species was completely killed in a short while. In Australia 

 the introduction of Dactylopius indicus from Ceylon, it is said, has 

 cleaned out 0. monacantha in sections where it was once a pest. 



While Dactylopius tomentosus did not originally attack the large 

 tree forms of Mexico at all. there are indications that lack of proper 

 host plants compels it to change its food habits. It is now attacking 

 nopal cardon {Opuntia streptacantha) . which for 10 years was en- 

 tirely immune in the Chico plantation. 



economic value 



MEDICINES 



To a limited extent Selenicereus {Cereus) graruMflorus and S. 



pteranthus (C. nycticallus) have been used in the preparation of 

 certain compounds. Other cacti are known to contain characteristic 

 alkaloids which from their peculiar action on the human system 

 may yet prove of value in treating special disorders. Most notable 

 of these forms is the so-called pellote (pronounced peh-yo'-te) or mes- 

 cal button, also known as the dumpling cactus (Lophophora williamsii 

 and L. leicinii). Since remote times the aborigines of North 

 America have used this plant in certain of their religious rites. 

 When the plants are eaten raw. dried, or fresh, with water, the optic 

 nerve is so affected that by closing the eyes the user is made to see 

 visions illuminated in the brightest of colors. An alkaloid of this 

 plant has been separated from it and found to contain the same prop- 

 erties. It is not impossible that in time it may be found of value in 

 the treatment of certain ocular disorders. However, no member of 

 the family seems as yet to have yielded a drug that has been used to 

 anv considerable extent as a medicine. 



