278 INSECTS 



is preferred, one pound of chopped tobacco stems may 

 be boiled in one gallon of water until a dark brown 

 extract is obtained, and this will control white fly, 

 mealy bugs and most of the other greenhouse pests, 

 provided it be frequently and thoroughly applied. It 

 stains delicate flowers and is apt to cause a little injury 

 to very delicate foliage, but in general it is safe on all 

 ordinary plants. The cost of tobacco dust or ground 

 tobacco is low enough to warrant its use in gardens 

 and fields, and we have no better remedy for root lice 

 on trees and plants; even the woolly apple louse suc- 

 cumbs to a liberal application. To reach such insects, 

 the soil must be removed to a depth of at least six 

 inches in a circle from eighteen to twenty-four inches 

 around the trunk, varying according to the size of the 

 tree, before a layer of ground tobacco is put on, and the 

 trench must be then filled up. The soil moisture and 

 rains extract the nicotine and bring it into contact 

 with the root lice. Stems, whole or coarsely chopped, 

 are of very little use, since the nicotine is extracted so 

 slowly as to be ineffective. Tobacco is also used in 

 greenhouses as a fumigant and is quite effective against 

 a great variety of pests. It may be burnt on a layer of 

 hot coal in an open stove, an extract may be smeared 

 on the pipes for slow evaporation, or paper-rolls soaked 

 in the extract may be burnt on wires suspended in 

 different parts of the house. And that brings up the 

 point that there are now on the market commercial 

 extracts under various names which, when only small 

 quantities are to be used, are cheaper and better than 

 can be made at home. They must, however, as a rule 

 be used at greater strength than recommended on the 

 labels in order to be thoroughly effective. 



Soaps are also used against plant lice and other 

 sucking insects and these have a much greater range of 



