MEASURES FOR INSECT CONTROL 



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of water, and this may be diluted, one to two parts of water 

 and ap])lied for leaf-sucking insects. 



Pyrethrum or Persian Insect Powder. — This is a very power- 

 ful insecticide when properly prc])ared, but loses its strength 

 when exposed to air, so that particular care should be taken 

 to keep it in a tightly closed receptacle or it must be used 

 when quite fresh. It is a powdered material derived from the 

 grinding of the leaves or flowers and buds of the Pyrethrum 

 plant, the main sup])ly coming from Dalmatia, buta consider- 



able amount being produced in California. It is a volatile 

 oil and it is the vaporization and contact of this which is 

 destructive to the insect. It may be used as a spray by the 

 dilution of one ounce of powder to two gallons of water, and 

 is available for saw-fly larvae and other pests upon currants, 

 gooseberries, etc., being especially valuable on account of 

 its not being poisonous to man or domestic animals. The 

 powder, blown into rooms is effective for the killing of 

 mosquitoes and flies, but for this i)urpose does not compete 

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