586 Bulletin 283. 



seeds of the crop, as, for example, the smut of oats and wheat, or the 

 pod spot of beans. In such cases it becomes necessary to treat the 

 seed to kill the fungus or to select seed free from the disease. Special 

 methods of cultivation, soil treatment, sanitation, etc., are means of 

 controlling these pests and maladies, to be practiced, as is spraying, 

 only in those cases in which they have been shown to be especially 

 applicable. 



To successfully apply these measures for control of a given disease, 

 certain factors must be taken into consideration. For example, in 

 spraying apple trees for scab, the stage of development of the buds, 

 blossoms, and fruit, together with the character of the weather rather 

 than the day of the month, must be the guide in making the application. 

 For nearly all fungous diseases spray before rains, not 



Things to be after. Fungous spores are scattered and germinate 



remembered, during rains, seldom after. Protect the plants by 

 having the mixture on when the rains come. Bordeaux 

 or lime-sulfur does not wash off easily. When spraying for insect pests 

 alone, apply the mixture after rains. Spray thoroughly. Every leaf and 

 fruit must be coated to be protected. Use a nozzle that gives a fine, 

 misty spray. That requires also good pressure behind the nozzle. The 

 amount of pressure required to do good work varies with the type of 

 nozzle. It should never be less than 75 pounds, and some types of 

 nozzles require 175 pounds to do best work. 



Timeliness and thoroughness are more important factors in the con- 

 trol of diseases and insect pests than are the particular mixtures of 

 poisons used. 



I. INSECTS AND THEIR CONTROL. 



M. v. SLINGERLAND, GLENN W. HERRICK AND C. R. CROSBY. 



For purposes of control, insects are divided into two great classes: 



^^^ A. Chewing insects, or those hav- 



^^^^^^^JIBM^X ing jaws by means of which they 



H|||HHHb^^^^L\ bite off and eat portions- of the tissues 



W^ «HI^^^^B^^k_ of the plant. Examples: Potato 



K;. ' ^^^^^^^^^^H beetle, canker-worm, and codling- moth 



f : ;^^|HH|9^I^^^^^^^^^^H caterpillar. . 



l^^^^^^^^^^^^H^^^B B. Sucking those fur- 



L^ '^Hl^H^WI^H^^Hii^H nished with a beak containing four 



P[(, ,y,._.4 plant-louse, one of tlte bristles united into a slender tube. 



sucking insects, showing the beak. The bristles are inserted into the 



