INSECTICIDES AND FUNGICIDES 269 



the advantage of remaining effective when diluted. It can, therefore, be 

 used on. foliage in summer for both scale insects and plant lice, and being 

 quicker in its action than tobacco extract, has advantages under some 

 circumstances over the extract for the prompt destruction of soft-bodied 

 insects. It is, however, more likely to do injury to plants, especially if the 

 emulsion is badly prepared, and this, together with the work required in 

 making it, leads practical men to neglect it whenever they can use some- 

 thing else. 



The standard emulsion is made of one-half pound of whale oil or 

 laundry soap dissolved in a gallon of boiling hot water, this to be added to 

 two gallons of coal oil, and the whole churned for ten minutes by passing 

 rapidly through a force pump. As thus made it can be diluted for use, 

 one part to ten of water. 



Crude Oils. — These are sometimes used for the same purposes as the 

 refined oil, and to render them easily mixed with water are sometimes 

 mixed with caustic potash, fish oil and crude carbolic acid, producing a 

 so-called miscible or soluble oil, which can be diluted with water for use 

 like the coal oil emulsion. 



Soaps. — Many of the soaps sold in our market can be used at times as 

 a means of lessening the injuries of insect pests. A good soapsuds fre- 

 quently and freely used on plants infested with aphides or scale insects has 

 a good effect, though not a very prompt one. Stronger solutions must be 

 used with some caution to avoid injury to foliage. When trees are dormant 

 very strong solutions (one or two pounds to a gallon of water) are sometimes 

 used on the trunks for scale and other insects. 



Whale oil soap or fish oil soap, as it is sometimes called, is to be pre- 

 ferred to most others because of its more even composition. It is particu- 

 larly good for use in making coal oil emulsion. 



Coal Tar. — In the early days of fruit growing in America this substance 

 was much used on the trunks of trees to prevent the ascent in the spring 

 of the wingless female canker worm moth. It proved to have an injurious 

 effect on the trees after a time, and hardened on exposure, so that the insects 

 could pass over the barrier. It was then used on bands of tin, and by 

 frequent renewal proved a useful check on the insect. But with the intro- 

 duction of arsenites and spraying machinery, it was given up for the more 

 convenient treatment. It is still used as a barrier, poured along the ground, 

 for chinch-bugs which are migrating from small grains to corn. Seed corn 

 may be treated with it before planting to deter wire worms and the seed 

 corn maggot from attacking the germinating seeds. The corn is first 

 immersed in warm water for a minute or two, then a couple of teaspoonfuls 

 of the tar are stirred quickly among the grain so as to bring a little in con- 

 tact with each seed. It dries over night so as to be ready for planting the 

 following day. The application does no harm to the germ, as has been 

 determined by germination tests of treated seeds. 



Borax. — This substance has often been recommended for roaches in 



