N«. 6. DEPARTMENT OF AGRICUL,TURE. 545 



it should be remembered that most substnnees that kill insects 

 will also kill plauts if applied in sufficient strength. Fortunately 

 I here is a safety limit of strength at which insects are killed and 

 jilauts are uninjured. Our object should be to apply insecticides of 

 such strength as to have the desired effect on (he pests, but to save 

 the plants. An insecticide should be applied at the proper time and 

 for a certain kind of insect, and should be selected in accordance 

 with the recommendations made for the destruction of the specific 

 kind of insect under contemplation. 



A. Internal Poisons or Stomach Poisons, for Chewing Insects. 



1. Paris Green. The poisons that contain arsenic are called Ar- 

 senites and Arsenates. Paris green is the arsenite of copper and 

 contains about G9 per cent, of arsenic. It can be applied as either (a) 

 a powder, or (b) in liquid. 



(a) Paris Green as a Powder: This is to be dusted on the plants, 

 but it should be mixed with some diluting powder in proportion of 

 one i>art of Paris green to from 20 to 50 parts of the dilutant. On a 

 small scale, flour is generally used, but air slaked lime, land plaster 

 and even road dust or wood ashes are good. It will adhere to the 

 leaves better if applied early in the morning while the dew remains 

 or just after a shower of rain. v>'hile they are yet damp. It is washed 

 ort" by a dashing rain and should' be repeated after each rainfall. If 

 there is no rain it is well to repeat the dusting about once every two 

 weeks. 



For applying dusts or powders a "powder gun" or bellows will 

 prove useful but not essential. Small hand "puffers" for this pur- 

 pose are common in stores. A good method is to put the powder into 

 a thin cloth sack or coffee bag, carry it over the plants to be dusted, 

 and pound it with sticks. Especial care should be taken to dust it 

 over the vines of jjlants for the young borers when they first hatch 

 and commence to eat their way toward the inside of the plant. This 

 is the only opportunity to kill them without cutting them out or 

 piercing them with a sharpened wire. 



(b) Paris Green in a Liquid: The Cucurbitaceous plants are very 

 tender and easily injured. Therefore Paris green can not be applied 

 to them in as strong a mixture as to apple trees, but it must be di- 

 luted, as for peaches and plums. The formula for vines is: 



One pound Paris green to 200 gallons of v/ater, or 4 ounces to 50 

 gallons. Stir the poison well into the water, then mix with a little 

 water an amount of air slacked lime equivalent to that of the Paris 

 green used, and stir the ''milk of lime" into the poisoned water. This 

 is to prevent burning the tender foilage. It MUST be applied as a 

 epray and not merely sprinkled on the plants. The work can pro- 



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