PLANT DISEASES AND INSECT PESTS 163 



suitable place for birds. Rotation aids in reducing the loss 

 from insects, because it provides for moving each crop to 

 a different field every year or two, and by the time the 

 insects get a start in one field the crop they are attacking is 

 moved to another field and largely escapes. Fall plowing 

 destroys many insects by destroying their winter quarters, 

 or by exposing the eggs or insects so that the weather kills 

 them. Cleaning up fence corners and rubbish destroys 

 good hiding places and winter quarters for many insects. 

 Birds eat great quantities of insects, and anything done to 

 protect or shelter them aids in controlling insects. 



Poisons for the biting insects are either sprayed or dusted 

 on the plants. The liquid spray is most common and gen- 

 erally most satisfactory. Paris green mixed in water in 

 the proportion of one pound of Paris green to fifty gallons 

 of water is one of the most common poisons. Arsenate of 

 lead mixed, three pounds to fifty gallons of water, is also 

 generally used. Bordeaux mixture, which is used as a spray 

 to destroy some of the plant diseases, see page 149, may be 

 used with either of these poisons in place of water. So one 

 may often spray for insects, like potato bugs, and plant 

 diseases, like potato blight, at one operation. 



Contact sprays for sucking insects may be made at 

 home or purchased. A very simple and satisfactory spray 

 for plant lice is soap solution, made by dissolving one pound 

 of laundry soap in fifteen gallons of boiling water. This 

 solution may be used any time, but is more effective when 

 warm. Tobacco extracts are sold commercially by druggists 

 in serveral different forms. From half a pint to a pint is 

 used in fifty gallons of water. 



The cotton boll weevil has done great damage to the 

 cotton crop. When this insect first appeared it was feared 

 it would completely destroy the cotton industry; but it 

 has become less destructive since cotton growers have 

 learned how to control it. Rotation of crop>s, thorough 

 cultivation of the cotton crop, and early planting of early 

 varieties have been found quite effective in controlling it. 

 Questions: 



1. Can you tell some of the characteristics of insects? What are 

 the four stages or changes that insects go through? 



