_Tobacco._--This is a valuable insecticide and is used in several forms.

As a _dust_ it is used extensively in greenhouses for plant-lice, and in nurseries and about apple trees for the woolly aphis. Tobacco _decoction_ is made by steeping or soaking the stems in water. It is often used as a spray against plant-lice. Tobacco in the form of _extracts,_ _punks,_ and _powders_ is sold under various trade names for use in fumigating greenhouses. (See page 188.)