REMEDIES AGAINST SCALE-INSECTS. 99 



If used in sufficient strength to kill Scale-insects, the hands and arms 

 must be protected from the liquid by rubber gloves, and care must also 

 be had to avoid inhaling the poisonous gases exhaled. 



In its active state the preparation is a depilatory, and by applying it 

 as a paste the hair upon any part of the body may be reduced to gela- 

 tine and removed. 



Bisulphide of Carbon. The few trials made of this substance have not 

 given very satisfactory results, and additional experiments are needed 

 to determine whether it can be safely and economically used as a remedy 

 for Scale-insects. Although a powerful insecticide, the extreme severity 

 of its action upon the trees and the cost of the materials detract greatly 

 from its value. It is an exceedingly volatile and explosive liquid, which 

 must be kept in tightly-sealed glass bottles, and the fumes cannot be 

 inhaled by man or other animals without danger. The bisulphide may 

 be emulsified with oils and milk or soap, but not more than three or 

 four fluidouuces should be contained in each gallon of the diluted wash. 



Appendix II, table 5, gives the result of some experiments with bi- 

 sulphide of Carbon. 



Sulphuric Acid. A single experiment with sulphuric acid, 4 fluid- 

 ounces .in 6 quarts of water, applied with a brush as far as possible to 

 all parts of a young tree, killed nearly all the Scale-insects, and very 

 nearly killed the tree. The bark was blackened but not destroyed, and 

 nearly all the leaves dropped. The tree, however, slowly recovered. 



Sulphate of Iron. This substance is exceedingly injurious to vegeta- 

 tion, but is, nevertheless, a very common ingredient of patent and pro- 

 prietary remedies. Its presence can be detected by the inky-black or 

 brown stains which it forms in the substance of the leaves and the rind 

 of the fruit. 



It does not affect the Scale-insect except by destroying the vegetable 

 tissues from which it gets its subsistence. 



Ammonia. With this in a pure state-no experiments have been made, 

 but to its presence in fermenting urine is probably due the insecticide 

 properties of the latter. Applications of urine have often been recom- 

 mended as a remed3 r lor scale, and are certainly not without value> but 

 if allowed to stand and ferment, and especially if soot or other absorb- 

 ents of the ammonia are mixed with it, it becomes highly injurious to 

 vegetation, and if applied at all should be greatly diluted. A mixture 

 of soot and fermented urine applied undiluted to a small orange tree 

 effectually cleared it of scales, but very nearly killed the tree. 



Silicate of Soda. This is a thick viscid liquid, sometimes sold as a 

 solid. It is readily soluble in water. When sprayed upon orange trees 

 it soon dries and forms a coating of gum which partially peels off, car- 

 rying with it many of the old dead scales and some living ones. When 

 applied in sufficient strength it kills most of the Coccids, but does not 

 destroy the eggs. It injures the plant more than kerosene, with which 

 it cannot be compared in efficiency or cheapness. The preparation is 



