THE CONTROL OF INJURIOUS INSECTS 395 



(/) Carbon Tetrachloride. — This liquid although not so active as 

 carbon bisulphide is not explosive. It may be used for fumigating 

 bins infested with insects, when applied at the rate of 2 lb. for 

 every 100 cu. ft. of space or 100 bu. of grain. 



4. The Application of Repellent Substances 



Several substances are known to act as ''repellents" to insects 

 and may sometimes be used to advantage in preventing insect attack 

 Among such substances are: (a) Bordeaux mixture; {b) tobacco dust 

 (c) carbolic acid emulsion; {d) kerosene; {e) turpentine; (/"), coal tar 

 {g) naphthaline; {h) zenoleum and creolin compounds; {i) tanglefoot 

 ij) carboHneum emulsion; {k) soap-carbolic-Paris green wash. 



(o) Bordeaux Mixture. — This fungicidal mixture keeps away flea- 

 beetles from potato leaves and striped cucumber beetles from pumpkins 

 and squashes when applied as a fine spray. It is prepared as follows: 

 Copper sulphate (bluestone), 4 lb.; quickHme, 4 lb.; water, 40 gal. 



CUSO4, 5H2O + Ca(0H)2 = Cu(0H)2 + CaSOi + 5H2O. 



2[Cu(OH)2, CUSO4] + CO2 = 2CUSO4 + Cu(0H)2 + CuCOs + H2O. 

 In mixing solutions of these two substances care must be taken that 

 they come together in a large quantity of water, and that enough 

 lime is present to act on all the bluestone. 



{b) Tobacco Dust. — In the case of certain garden crops fine sprin- 

 kling of the ground when moist with refuse tobacco dust not only 

 fertilizes the soil but also repels the striped cucumber beetle and the 

 melon aphis. 



{c) Carbolic Acid Emulsion. — Carbolic acid is a repellent, as well as 

 an irritant and stomach poison, and in various forms is used for the 

 control of insects. Reference has already been made to its use as a 

 contact insecticide. As a repellent it is added to a solution of wash- 

 ing soda or lye as a protective wash against borers in orchards and 

 shade trees; as an emulsion with soap against root-maggots of cab- 

 bage and onion; and often also used in poultry house against biting 

 lice and mites. 



(</) Kerosene, (e) Turpentine and (/") Coal tar are sometimes mixed 

 with saw-dust, sand, or other materials; when placed around plants or 

 seeds they are said to have a repellent action toward insects. 



