INSECTICIDES, PREVENTIVES, AND MACHINERY. 441 



insects are supplied, but very fine particles often make their way 

 through them. It is important, therefore, if tobacco is to be 

 used dry, that it be in as fine a condition as it is possible to ob- 

 tain. This applies even where it is used on the surface of the 

 ground around cabbage plants. As a decoction its range of 

 usefulness is greater. It is fatal to a large number of caterpillars 

 of the smaller moths, both as a contact and as a stomach poison, 

 and cranberry growers in Massachusetts use great quantities of it, 

 at the rate of one pound to one gallon of water, against ' ' vine- 

 worms" and "fire-worms." Stems and other refuse are just as 

 good as leaf tobacco for this purpose, and the usual method is to 

 boil down the coarsely chopped stems until a deep brown extract 

 is obtained. This is also effective against plant-lice. Ground 

 tobacco may be applied on the surface around trees infested with 

 root-lice, and the result will be beneficial, especially in light soil. 

 As against the peach-root lice, tobacco has been employed by 

 first trenching around the base of a moderately large tree at a 

 distance of two feet from the trunk, and applying the tobacco 

 dust in the trench. To obtain the greatest effect there should be 

 an early application of water, either in the form of rain or arti- 

 ficially, to dissolve the nicotine and carry it into direct contact 

 with the root-feeding lice. As tobacco is also a fertilizer, quite 

 rich in potash, the benefit to the plants is doubled where the 

 material is applied to the soil. As a stomach poison tobacco is 

 not often to be recommended, but as a contact poison it is fre- 

 quently the most cleanly, and is a favorite remedy in the green- 

 house. Besides the methods already indicated, it may also be used 

 in the form of smoke ; burning or steaming it, and sending the 

 impregnated vapor into the conservatory or hot-house. Tobacco- 

 smoke is quickly fatal to all insects that breathe it, but plants ex- 

 posed to it for any great length of time are also likely to suffer. 

 No specific directions as to the quantity of tobacco to be used 

 can be given, and it will require practical experience to acquire 

 the knowledge for each case. Good effects can be obtained in 

 greenhouses by simply placing tobacco-stems on the benches, or, 

 if the plants are potted, the pots may be set in a bedding of 

 stems, or the stems may be kept upon the pipes heating the 

 house, and this will give a sufficient impregnation to the air to 

 discourage many insects, while there is no danger to plants. 



