Elementary principles of agriculture Elementary principles of agriculture : a text book for the common schools . elementaryprinci02ferg Year: 1913 Insects on the Farm 165 (a) Food, or Internal Poisons, are substances which poison by being taken into the digestive tract of the insect. This class includes various arsenical compounds, such as Paris green, London purple, lead arsenate. Poisons of this class are used for insects that chew their food, as the leaf-eating forms, unless the use of the poison i» W-r*'^ Fiii. Iiil2. Sprayiiii; in iUl- late tliriiiant .-^.ason. renders the plants dan
Elementary principles of agriculture Elementary principles of agriculture : a text book for the common schools . elementaryprinci02ferg Year: 1913 Insects on the Farm 165 (a) Food, or Internal Poisons, are substances which poison by being taken into the digestive tract of the insect. This class includes various arsenical compounds, such as Paris green, London purple, lead arsenate. Poisons of this class are used for insects that chew their food, as the leaf-eating forms, unless the use of the poison i» W-r*'^ Fiii. Iiil2. Sprayiiii; in iUl- late tliriiiant .-^.ason. renders the plants dangerous for food, such as cabbage. (b) Contact Poison. Substances that destroy by attacking the body of the insect, such as washes of caustic alkalies, oils, etc. They are used for sucking in- sects, , those having beaks, such as the San Jose scale. (c) Fumigation Poisons. Substances which enter the breathing pores of the insect and cause death by poison- ing or suffocation. Smoke, and the deadly hydrocyanic acid gas, Pyrethrum, or 'insect powder,' and carbon bisulphide, belong to this class.
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