52 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



as insecticides and many of these have value. Whale-oil or fish- 

 oil soap is more widely used as an insecticide than other kinds. It 

 may be prepared at home, using about twenty pounds of the oil, 

 which should be saponified by stirring into it a solution of 5 to 6 

 pounds caustic soda in a half-gallon of water. These soaps may 

 be found on the market, ready for use and in normal times are 

 fairly cheap. They are widely used in nurseries to keep young 

 trees free from scale and aphids. 



14. Carbolic acid emulsion is used for various purposes. It is 

 valuable to kill aphids and soft-bodied scale-insects and is used 

 also for insects which attack the roots of some garden crops. It 

 is made from whale-oil soap, 40 Ibs., dissolved in 40 gallons of 

 water and boiled for twenty minutes with 5 gallons crude carbolic 

 acid. This product is diluted at the rate of one gallon to 15 or 

 20 gallons of water for use. 



3. Repellants 



Repellants include any substance which may be applied to a 

 plant or animal to prevent insect attack. A popular notion that 

 any vile-smelling substance will repel insect attack seems to have 

 very little evidence in its support. Tobacco dust, air-slaked lime, 

 or even fine road dust, thoroughly covering a plant will prevent 

 the attack of various flea-beetles and leaf-eating beetles, but to be 

 successful the plants must be frequently dusted and kept well cov- 

 ered. Bordeaux mixture, our most widely used fungicide, when 

 liberally sprayed on potatoes and tomatoes, acts as a repellant to 

 the little black flea-beetles which often seriously damage the 

 young plants. 



The various fly-sprays which are used for spraying cattle to 

 prevent the annoyance of flies act merely as repellants. 



Fruit-trees are often painted with a thick soap solution con- 

 taining 1 pint of crude carbolic acid to 10 gallons as a repellant 

 for the adult borers which lay their eggs on the bark. 



A substance which has come into prominence in the fight 

 against the gypsy moth in New England is tree tanglefoot, a sticky 

 substance the same as is used to coat fly-papers. This comes in the 

 form of a very sticky paste, a band of which is placed around the 

 trunk of the tree and which prevents the ascent of caterpillars, as 



