392 ECONOMIC ENTOMOLOGY 



quenlly on aphids, slugs, and some household pests, where operations 

 are confined to a small area. 



It may be used either as a spray or in the dry form. As a spray 

 it should first of all be made into a paste in a small quantity of water 

 and afterward diluted to the proper strength, viz. : i oz. to 3 gal. 

 of water. When used dry, i part of powder is thoroughly mixed 

 with 4 parts of flour, and kept in a tight can for a day. The mixture 

 is dusted on either by a bellows or through a coarse bag, on account 

 of the fact that the essential ingredient is a volatile oil. 



Pyrethrum loses its strength on exposure to the air; the can must, 

 therefore, be kept tightly closed. 



(g) Lime. — Air-slaked lime is effective against slugs and other 

 soft-bodied larvae. It should be applied as a very fine dust. 



Some investigators report beneficial effects from the application 

 of thick lime-wash about onion plants as soon as they are up as a 

 protection against the onion maggot. 



Professor Parrott of the Geneva Agricultural Experiment Station 

 finds that lime with nicotine is much more effective against aphis, 

 leaf -hopper and pear psylla than nicotine alone, or soap, or oil emulsion. 



{h) Commercial Sodium, Fluoride. — This substance, both a poison 

 and a contact insecticide, is effective against cockroaches, chicken 

 lice and other insects when applied^ pure or mixed with flour or plaster, 

 as a fine dust by means of a dust blower. 



{i) Carbolic Acid Emulsion.~¥ or the control of root-feeding 

 larvae such as onion maggots and radish maggots, an emulsion of 

 carbolic acid has given good results. It is prepared by dissolving 

 I lb. of hard soap in i gal. of hot water and adding i pt. of crude 

 carbolic acid. The mixture is agitated until a thick, emulsion is 

 produced. This is the stock solution, and is diluted with 20-30 

 parts of water for use. A tablespoonful is poured about the base of 

 the plant to prevent egg-laying, and at the same time to kill the newly 

 hatched larvae. 



(j) Scale insects on ferns are treated effectively by the use of i 

 part fir-tree or lemon oil to 15 or 20 parts of water. 



{k) Cattle Dips.— The most widely used methods of controlling 

 cattle-scab diseases are: 



I. Dipping the animals in lime-sulphur or nicotine solutions 

 twice, ID to 14 days apart. Dipping plants are arranged so 



