338 SCHOOL ENTOMOLOGY 



oughly covering a plant will prevent the attack of various 

 flea-beetles and leaf-eating beetles, but to be effective the 

 plants must be frequently dusted and kept well covered. 

 Bordeaux mixture, our most widely used fungicide, when 

 liberally sprayed on potatoes and tomatoes, acts as a repel- 

 lent to keep off the little black flea-beetles which often seri- 

 ously damage the young plants. 



The various fly-sprays which are used for spraying cattle 

 to prevent the annoyance of flies act merely as repellents. 

 Blue ointment is sometimes used against animal parasites, 

 evidently affecting them as a repellent. 



Fruit trees are often painted with a thick soap solution 

 containing 1 pint of crude carbolic acid to 10 gallons as a 

 repellent for the adult borers which lay their eggs on the 

 bark. 



Naphthalene or moth balls and similar substances used 

 for driving away household insects are effective as repellents. 



Various proprietary insecticides are frequently offered 

 for sale with wonderful claims for their effect as repellents, 

 but only in rare cases are they of any value except for use as 

 dust as already suggested.* 



* For further discussion of insecticides see Farmers' Bulletin 127> 

 U. S. Department of Agriculture. 



