INSECTICIDES AND THEIR USES 3I 



Stronger mixture can be used on resistant plants like potato, and 

 a weaker solution (i to 200) must be made for young and 

 delicate foliage. 



For the proper preparation and application of this and other 

 sprays a sprayer or spray pump is necessary. The Paris green 

 should first be mixed with a small quantity of water into a thin 

 paste before the bulk of the water is added, and should then be 

 thoroughly mixed by churning in the force-pump. As the mix- 

 ture is only a mechanical one the Paris green tends to sink to 

 the bottom, and to avoid this it must be constantly stirred while 

 being applied, otherwise the mixture near the bottom of the 

 tank or reservoir will become so strong as to scorch the foliage. 

 Care should be exercised in the purchase of a spray pump that 

 it be equipped with a proper agitator. 



When applied dry, it is generally mixed with from 10 to 20 

 parts of flour, plaster, "or lime. This remedy affords best results 

 early in the season on young plants. It should be dusted on 

 preferably when the dew is on, or after a shower, and by means 

 of powder guns or bellows, or the so-called "dust-spray" ma- 

 chines, so as to cover the plants and leave as little surface as 

 possible for food for the first-appearing insects. 



It is often advisable to use P)ordeaux mixture in combination 

 with an arsenical, especially if a disease is present. This is 

 a valuable insect repellent as well as a standard fungicide, and 

 it operates also against different forms of blight and other 

 diseases which may threaten the crop. It is used as a diluent 

 instead of water and in the same proportions, and prevents 

 scorching. Its preparation is discussed on page 28. 



Paris green is more usually recommended for general pur- 

 poses because it is known to most farmers, can be obtained in 

 drug stores anywhere, and because of its supposed cheapness. 

 Its use, however, is being superseded in some degree by arsenate 

 of lead and other arsenicals. 



Paris green is very frequently adulterated by unscrupulous 



