86 



INJURIOUS INSECTS. 



of good quality. It also deteriorates very quickly when exposed 

 to the air. On these accounts it is often very difficult to get sat- 

 isfactory results from that obtained at the stores. When used it 

 should be diluted v/ith about five times its bulk of flour, with 

 which it should be kept in a tight vessel for at least twenty-four 

 hours before using in order to get best results. When thus con- 

 fined it takes up the poisonous principle of the pyrethrum. It 

 should always be kept in an air-tight receptacle. 



Paris green is a refuse product composed of arsenious acid 

 and copper and is probably as safe as any arsenic compound. 

 It is only very slightly soluble in water, and is used with water 

 at the rate of one pound to one hundred or more gallons of 

 water; it is also used when mixed with dry substances, at the 

 rate of one pound to fifty pounds of flour or one hundred pounds 

 of land plaster, road dust or sifted coal ashes. In using it with 

 water the addition of an equal amount of milk of lime often 

 prevents injury to leaves. 



London purple is composed of arsenious acid and lime. It is 

 often much cheaper than Paris green but varies more in its com- 

 position. On account of its being lighter than Paris green it 

 does not settle so quickly when put in water. It is used in the 

 same manner as that substance. When used in water an equal 

 amount of milk of lime should always be added to neutralize the 

 free acid which it sometimes contains in injurious quantities, 

 and which may burn the foliage of tender plants. London purple 

 adheres to the foliage of plants longer than Paris green. 



Tobacco 's very useful for destroying some kinds of insects 

 in the garden and greenhouse. It is especially effective aginst 

 plant lice and soft-skinned hairless caterpillars. Where smoke 

 from it can be confined around the plants, as in greenhouses and 

 hotbeds, it is common to use it in a smudge, but when thus used 

 it should be kept from blazing. It is also used in powdered form 

 to keep off seme insects. A more common and effective way of 

 using it, is as a decoction in water at the rate of one pound of 

 tobacco stems, leaves or dust to two gallons of water. The 

 tobacco should be boiled in the water for twenty minutes. When 

 cold the decoction should be used undiluted with a syringe, spray 

 or otherwise. The decoction will not keep more than a few days 



