CHAPTER XX 

 INSECTICIDES, FUNGICIDES AND DISINFECTANTS 



159. Two Classes of Injurious Insects. The insects 

 which are injurious to growing or stored crops may be 

 separated into two main classes : insects that bite, and those 

 that suck. Different remedies must be used in combating 

 each class. Among the most common biting insects are the 

 codling moth, potato bettle, the flea beetle, the grass- 

 hopper, the tussock, brown tail, and gypsy moths, the plum 

 curculio, and the various caterpillars. The biting insects 

 are destroyed by spraying the plants eaten with some 

 poisonous material that will be taken by the insect with its 

 food. The materials commonly used for this purpose are 

 compounds of arsenic which has decided toxic effects. Some 

 of these substances are arsenate of lead, Paris green, green 

 arsenoid, London purple, and arsenate of lime. The last 

 named is a product recently put on the market. 



Sucking insects draw the plant juices from the leaves 

 and the bark; the most common are plant lice, the Chinch 

 bug, San Jose scale, scurfy scales, etc. They are killed by 

 materials that close their breathing pores, fill the surround- 

 ing atmosphere with poisonous fumes, or kill by reason of 

 their caustic properties. The following materials are used 

 for this purpose: kerosene emulsion, soaps, lime-sulphur 

 mixtures, nicotine sulphate solutions, carbon bisulphide, 

 and hydrocyanic acid gas. 



160. Injurious Fungi. Injurious fungi are minute 

 vegetable organisms that attack living tissue. The fungi- 

 cides include Bordeaux mixture (made from milk of lime and 

 copper sulphate), lime-sulphur, sulphur, copper sulphate, 

 ammoniacal copper carbonate, and formaldehyde solutions. 



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