56 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



face soil and applying a liberal dressing of the dust and then 

 covering. The rains leaching through the tobacco carry the 

 tobacco water to the affected roots and destroy or repel the 

 aphides. 



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 

 it will remain sticky for some weeks. It may be used in the same 

 way to prevent the wingless female canker worms and other 

 wingless insects from ascending trees, or to prevent the ascent of 

 caterpillars on unaffected trees. 



Various proprietary insecticides are frequently offered for sale 

 with wonderful claims for their effect as repellants, but only in rare 

 cases are they of any value except for use as a dust as already sug- 

 gested. One of the most common fakes of this sort is that of the 

 itinerant tree-doctor who offers to bore a hole in a tree and plug 

 it with sulfur or other offensive compounds, which will effectively 



