INSECTICIDES AND FUNGICIDES 1009 



tobacco is grown and the midribs can be easily secured is one of the very 

 best insecticides for uses of this sort. The whole leaf makes a somewhat 

 stronger extract (0.12 per cent) as determined by tests recently made at 

 the Virginia Station. Soaking seems to extract as much of the nicotine as 

 boiling. When plants are to be treated on a larger scale it becomes impor- 

 tant to know just how much nicotine is present in a wash, and manufactured 

 extracts, some of them containing 40 per cent of nicotine, are demanded. 

 For the apple leaf louse, the lettuce louse, the rose aphis and other similar 

 pests, these extracts are safe and effective. For thick-skinned insects they 

 are not so satisfactory. 



Tobacco is often used in other ways as a remedy for insect injuries, 

 but is open to some objections when so employed. Florists have long used 

 the midribs (often called "stems") for making a smudge for the destruction 

 of plant lice. The tobacco is simply burned in a perforated iron vessel. 

 The smoke leaves a strong smell of tobacco on flowers, which is sometimes 

 objected to by buyers. The odor can be avoided by using the extract 

 diluted with water and driven off as a vapor by dropping a hot iron into a 

 pan containing it. 



Pyrethrum. — Under the name Persian insect powder or simply insect 

 powder this insecticide is to be obtained from most dealers in drugs. It 

 is a brown powder made from the flowers of a rather handsome plant of 

 the sunflower family (Compositce). Its beauty leads florists to propagate 

 it, though few who grow the plant know that it has any relation to the 

 powder sold in drug stores. It comes to us from the East, and the pow- 

 der commonly sold here is imported, though an effort has been made in 

 the west coast states to manufacture the powder in this country. 



The powder is thought to give off a volatile oil which penetrates the 

 breathing tubes of insects and thus by some irritating or suffocating effect 

 overpowers them. It is effective either dry, in water or when burned to 

 produce a smudge, but must be fresh. It loses much of its effectiveness if 

 kept in open packages. Though rather costly for use on field crops, it has 

 a place in the household at times, and may sometimes be profitably resorted 

 to for limited outbreaks of garden pests. Unlike most other insecticides, 

 this one is not hurtful to man; at any rate, not more so than snuff. 



White Hellebore. — This is another vegetable product, being the 

 pulverized rootstocks of a plant (Veratrum album) of the lily family, 

 occurring in Europe and northern Africa. It is used in this country for 

 the rose slug, either dry or in water, in the latter case about two heaping 

 tablespoonfuls being stirred into a wooden bucketful (2| gallons) of water. 

 It is a stomach poison and also a contact insecticide. 



Old samples when not kept in airtight receptacles lose their virtue and 

 tend to discredit this vegetable poison as a remedy for pests. 



Coal Oil. — This oil has become well known as an insecticide in the 

 form of an emulsion. It is a good contact insecticide, serving the same 

 purpose as lime-sulphur wash in the destruction of scale insects, and having 



64 



