PYRETHRA. 379 



5. Cuprlc Insecticide Boiiillie. — Treat by boiling from five to 

 ten minutes or by maceration for twenty-four hours in the cold, 

 3-4 lb. of pyrethra powder in 10 gallons of water, and mixing this 

 extract with a cupric bouillie by running it into the concentrated 

 bouillie. This bouillie has the advantage of acting both on the mildew 

 and the altise of the vine simultaneously. 



6. Alcohol and Carbon Disulphide Extract. — Treat 7 oz. of 

 pyrethra powder by maceration for eight days in a mixture of 7 oz. of 

 ether, 25 oz. of carbon disulphide, and 75 oz. of alcohol, 86° B. (all by 

 weight). Filter afterwards (Pratigeon). 



7. Pyretkra-petroleum Emulsion. — Emulsify petroleum in an 

 aqueous pyrethra extract. This emulsion is recommended by Webber 

 against cochineal. 



Properties. — Pyrethra powder forms a very fine light powder, 

 the insecticidal principles of which are volatile. Old powders are 

 dead and inert. 



Action on Plants. ^ — Pyrethra powder has the great advantage 

 over insecticides, such as petroleum, carbolic acid and others, of having 

 no injurious action on the leaves ; even the soapy extracts if they do not 

 contain too large a dose of soap are without injurious action on plants 

 (Fleischer). 



Action on Insects. — The intensity of the action depends on the 

 freshness of the pyrethra powder. The insecticide action of the 

 powder sold under the name of bug powder has been known for a long 

 time. If it be not preserved in a well-closed bottle, its insecticidal 

 power departs ; moreover, its action is of very short duration, the active 

 principles being very volatile. Carapaceous insects are generally in- 

 sensitive to this insecticide ; it is not so with soft-skinned insects and 

 larvae not protected by a hairy down, these succumb readily. The 

 different soapy and alcoholic extracts are much more active owing to 

 the substances which they contain, which moisten the insects touched 

 more perfectly than aqueous extracts. 



Use. — -As powder pyrethra is in domestic use to treat plants in pots 

 infested by lice and to free them from vermin. The extracts would 

 find an extensive use if they were cheaper and their action less vari- 

 able according to whether the pyrethra bought is fresh or old. 



Leptinotarsa decemlineata (Colorado beetle). — Alvood found that if 

 the powder is inert against adult insects, it kills 50 per cent of the 

 larvae. 



Saperda Populnea, L. (the poplar borer). — To destroy the larvae 

 of this Coleoptera, Mohr advises to inject his extract No. 4 (p. 378) into 

 their burrows by means of a caoutchouc drill guided by an iron wire. 

 The amount should be such that the liquid flows from the orifice. After 

 a quarter of an hour all the larvae leave the holes and can be crui^hed. 

 The same process is used to destroy the caterpillars of Cossus and of 

 Sesia ; the latter dies in the holes. 



Haltica ampelophaga (altise of the vine). — Pyrethra is regarded, 

 as an excellent medium for getting quit of the altise of the vine, and 

 altises in general, 12-15 per cent of pyrethra powder with ordinary 

 sulphur or Apt sulphur to overcome simultaneously the oidium and 



