376 MANUAL OF VEGETABLE-GARDEN INSECTS 



nicotine in the volatile form. It is intended primarily for use 

 in greenhouses. Strips of paper soaked in this i)reparation are 

 smudged in greenhouses to destroy aphids. 



Tobacco is also used in the form of a dust for the same pur- 

 pose. It is especially valuable against root-lice on asters and 

 other plants. Tobacco extracts can be made at home by 

 steeping tobacco stems in water, but as they vary greatly in 

 nicotine content and are sometimes likely to injure tender 

 foliage, it is better to buy the standardized extracts. 



Bordeaux m ixture . 



Bordeaux mixture is widely used on potatoes and many 

 other plants for the prevention of fungous diseases. In addi- 

 tion to its fungicidal properties, it also acts as a deterrent to 

 many insects, especially flea-beetles. Arsenate of lead, paris 

 green and "Black Leaf 40 '' may be used in combination 

 with it. 



Bordeaux mixture is prepared by mixing a solution of copper 

 sulfate, CUSO4, and milk of lime (calcium hydroxid) according 

 to the following formula : 



Copper sulfate 4 pounds 



Lime 4 pounds 



Water 50 gallons 



In some cases a weaker mixture is used, containing 3 pounds 

 of copper sulfate and lime respectively. These formulas are 

 often abbreviated thus : 4-4-50 and 3-3-50. 



When needed in large quantities, borfleaux mixture is most 

 conveniently prepared by using stock solutions of copper 

 sulfate and milk of lime and storing them in tubs on an elevated 

 platform from which the desired quantity of each can be easily 

 drawn off into the spray tank. 



The required quantity of copper sulfate sh )ul(l be dissolved 

 in water in the proportion of one pound to one gallon. This 



