1046 DISEASES AND INSECTS 



DISEASES AND INSECTS 



headed by the distance around the tree intersects the 

 horizontal line of figures corresponding to the distance 

 over. For certain insects it is not advisable to use the 

 full dosage schedule. 



Sodium cyanide (NaCN) is coming into use as a sub- 

 stitute for potassium cyanide. When pure, this com- 

 pound contains 53 per cent of cyanogen; that is, about 

 33 per cent more of cyanogen than is present in potas- 

 sium cyanide. It is customary to indicate the strength 

 of sodium cyanide in terms of potassium cyanide; that 

 is, pure sodium cyanide is said to be 133 per cent pure. 

 This means that 100 pounds of sodium cyanide will 

 yield as much cyanogen as 133 pounds of potassium 

 cyanide. For fumigation purposes, sodium cyanide 

 should be at least 124 per cent pure and should not 

 contain more than 1 per cent of common salt. 



Because of the greater content of cyanogen of 

 sodium cyanide, a smaller quantity is required. The 

 chemicals should be combined in the following pro- 

 portions: Sodium cyanide, one ounce; sulfuric acid, 

 one and one-half fluid ounces; water, two ounces. 



The following dosage schedule corresponds to the 

 one given above for potassium cyanide: 



Dosage chart for fumigating citrus trees with potassium cyanide (Bureau of Entomology, United 

 States Department of Agriculture). 



1325. A fumigating tent (Morrill system). 



often. It is always well to smoke through two consecu- 

 tive days, for the insects which persist through the first 

 treatment, being weak, will be killed by the second. 



If the plants are wet, 

 the smoke is more 

 likely to scorch them. 

 The smudge often 

 injures flowers, as 

 those of roses and 

 chrysanthemums. In 

 order to avoid this 

 injury, the flowers 

 should be covered 

 with paper bags. 

 Violet plants are very 

 liable to injury. 



Tobacco fumes can 

 be more conveniently 

 generated by burning 

 strips of prepared 

 nicotine paper, or by 

 vaporizing a concen- 

 trated aqueous solu- 

 tion of nicotine over 

 alcohol or special 

 kerosene lamps. 



Bisulfid of carbon is 

 a thin liquid that 

 volatilizes at a very 

 low temperature, the 

 vapor being very de- 

 structive to animal 

 life. It is exceed- 

 ingly inflammable, 

 and should never be 

 used near a lamp or 

 fire. It is sometimes 

 used for the control of 

 certain root insects. 

 It is poured into holes 

 made around the in- 

 fested plants, and 

 these are then imme- 



Nicotine preparations. Tobacco is used in various diately closed up causing the fumes to permeate the 

 ways in fumigating greenhouses. For smoking or soil in all directions. 



smudging greenhouses, tobacco-stems are burned 

 slowly. Best results are secured when a sheet-iron 

 vessel made for the purpose is used, having holes in the 



Against weevils infesting stored grain and seeds, 

 carbon bisulfid is effective at the rate of five to eight 

 pounds for each 1,000 cubic feet, provided the applica- 



bottom to supply draft. A quart of live coals is placed tion is made while the temperature is not below 65 F. 

 in the bottom of the vessel, and about a pailful of Make the bins as tight as possible. If bins are only 

 tobacco-stems is laid on them. The stems should not 

 blaze, but burn with a slow smudge. If they are 

 slightly damp, better results are obtained. Some 



single sheathed with common flooring use twenty to 

 twenty-five pounds carbon bisulfid. Let the fumigation 

 continue for at least twenty-four hours. Care should be 



plants are injured by a very heavy smoke, and in order taken not to apply carbon bisulfied when there is indica- 

 te avoid this injury, and also more effectually to destroy tion of heating in the grain. C. R. CROSBY. 

 the insects, it is better to smoke rather lightly and ROBERT MATHESON. 



