SOAP SOLUTIONS AND EMULSIONS, 329 



8. Dissolve 5 lb. of soft soap in 6| gallons of water, add thereto 



2 gallons of ordinary 90 per cent alcohol and 1 gallon of amylic 

 alcohol. 



9. Infuse 3 lb. of tobacco for some time in 5 lb. of amyl alcohol, 

 and 2 lb. of ordinary alcohol ; add a solution of 4 lb. of soft soap, then 

 make the whole up to 10 gallons (Muhlberg). 



These emulsions cannot be further dwelt upon here, each one will 

 be described under the heading of the insecticide with which it is 

 mixed. 



Action of Soap on Plants. — Soaps are more injurious to trees the 

 more caustic alkali and alkaline carbonates they contain. Solutions 

 of Marseilles soap (hard soap) are less injurious than soft soap ; the 

 latter becomes injurious, according to plant treated, from 0-66 per cent ; 

 it is dangerous to flowers from 1-32-2-5 per cent, for soapy sprayings 

 prevent them from producing fruits ; finally, it attacks the skin of stone 

 fruit, and injures the leaves when tender. Used in winter of great 

 strength (18-2-4 per cent) soap renders the trees sterile ; this is not the 

 case with 6-12 per cent solutions, except for the peach. Mixtures of 

 soap and alcohol are slightly more injurious than aqueous solutions of 

 soap, and when concentrated may kill the tree, but it is more especi- 

 ally mixtures containing tobacco which are dangerous and should be 

 used with care. 



Action on Insects. — -Soap in solution acts energetically on soft- 

 skinned insects and their larvae. A 2 per cent solution acts on cater- 

 pillars, larvffi of wire-worms, etc. Strong solutions of soap also act on 

 protected insects, such as the cochineals. Marlatt found that, used 

 on trees in winter, a 24 per cent solution of ordinary white soap killed 

 more than 97 per cent of the San Jose louse ; an 18 per cent solution 

 killed more than 95 per cent ; a 12 per cent solution moi'e than 90 

 per cent ; a 6 per cent solution more ihan 20 per cent ; and a 



3 per cent solution more than 10 per cent. Fish oil soaps are less 

 ■energetic. An 18 per cent solution only kills 50-75 per cent ; and a 

 12 per cent solution only 20 per cent. Whale oil soap solutions of 

 20-30 per cent kill 90-100 per cent of San Jose louse. In these 

 mixtures soap whilst an insecticide, generally only acts by bringing the 

 parasites in better contact with the insecticide and by increasing its 

 adherence. 



Use. — To dissolve the soap, or dilute preparations containing soap, 

 it is well only to use rain or distilled water, to prevent the lime of 

 ordinary water from precipitating lime soaps, which encrust the spray- 

 ing machines. 



Cryptogamic Diseases. — SpJicerotheca pannosa (rose mildew). — 

 To overcome this fungus use a 2 per cent solution of soft soap (Vesque). 



Mildeir of Phlox Drummondii and of Verbenas. — Halsted and 

 Kelsey overcome this disease by a solution of 3 lb. of rosin [? soap] in 

 10 gallons of water. The plants were sprayed twenty-six times from 

 27 November to 1 April. The action of an emulsion of petroleum 

 3 gallons, rosin soap 2 lb., water 100 gallons, was much more efficient, 

 even when diluted three times further. 



Insects. — Tomicm dispar, Bostrichus dispar (the apple l)ark 



