INSECT ENEMIES AND DISEASES 89 



with a direct nozzle to churn or agitate violently for 5 or 

 10 minutes, or until the mixture is of the consistency of 

 thick cream. If thoroughly emulsified the oil will not 

 separate and the stock solution may be kept almost in- 

 definitely. Various dilutions, ranging from 10 to 20 parts 

 of water, with one of the stock solution, are used for 

 various sticking insects. It is essential, of course, that 

 the emulsion come in contact with the enemy. This is 

 not always easy to accomplish, especially when the in- 

 sects are on the undersides of the leaves. 



133. Carbolic acid emulsion. As a contact poison and 

 a repellent carbolic acid emulsion is valuable in combat- 

 ing root maggots of various crops, such as onion, radish 

 and cabbage. It is made in the same manner as kerosene 

 emulsion (132), by using I pound of soap, I gallon of 

 water and i pint of crude carbolic acid. 



134. Tobacco is used in various forms. The powder is 

 often effective in destroying plant lice. Stems are some- 

 times strewn along the lines of peas to repel the pea 

 louse. Tobacco decoction, made by steeping or soaking 

 the stems in water, is an excellent insecticide for plant 

 lice. Numerous nicotine extracts and powders have been 

 placed on the market and are used for the various species 

 of aphides. 



135. Soaps. Whale-oil soap, I pound dissolved in 5 to 

 7 gallons of water, makes a useful insecticide to control 

 aphides and other minute insects. Hard and soft soaps 

 may be substituted, but whale-oil soap makes a more 

 effective spray. 



136. Miscellaneous insecticides. Numerous other ma- 

 terials are sometimes used in arresting the ravages 

 of injurious insects. Lime, ashes, bordeaux mix- 

 ture and sulphur may be classed among insect 

 repellents. A formalin solution prepared by mix- 

 ing I pint of a 40 per cent solution with 30 to 40 gallons 

 of water is valuable in treating potatoes both for scab 



