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REPORT OF THE ENTOMOLOGIST AND BOTANIST 73 



SESSIONAL PAPER No. 16 



In all these poisons, arsenic is the essential ingredient, and other chemicals are 

 mixed with the arsenic for the purpose of preventing it from injuring vegetation. 

 There are many spraying compounds which contain arsenic, some of which are sold 

 ready-made, and many others are made at home by combining the necessary ingre- 

 dients. 



Paris Green. — Undoubtedly the best known, and in many respects the safest, 

 I'o'son to use is Paris green. It has passed through many years of trial, is well 

 known, has a distinctive colour, and is a definite chemical compound containing 58 'BS 

 per cent of arscnious oxide, 31*29 per cent of copper oxide, and 10 "06 per cent of 

 acetic acid. It is, therefore, an aceto-arsenite of copper. It is soluble in ammonia. 

 Paris green, if demanded, is now obtainable pure in all parts of Canada; but, as there 

 is sometimes an adulterated article found in the market, it is wisest always to add an 

 tqual amount, with the Paris green, of freshly slaked lime, when the free arsenic will 

 combine with the lime, and it can then be used safely at the rate of one pound of Paris 

 ^rocn in IGO gallons of water on all vegetation, and, for a dry application, 1 pound 

 of Paris green in 50 pounds of flour, land-plaster, slaked lime or some other perfectly 

 dry powder. 



As a general i)rineiple, lime should be always used with Paris green whenever it 

 is applied in a liquid insecticide. Paris green is very heavy, and the particles quickly 

 sink to the bottom of any liquid with which it is mixed. This makes constant stirring 

 necessary. Paris green does no"t dissolve in water, and is merely mixed with water 

 to facilitate its even distribution on vegetation in the very small quantities that are 

 necessary to destroy insects. The finer the poison is ground the quicker its effect 

 on the insects which eat it, because the minute crystals are more rapidly dissolved 

 by the digestive juices in the stomachs of the insects. The finer it Is ground the better 

 also it will remain suspended in a liquid application. Por most insects, one ounce of 

 Paris green in 10 gallons of water is the standard strength; but some plants with 

 coarse "foliage, such as the potato, will stand double that strength. 



Arsenate of Lead.— A poison which has come into much notice since the work of 

 the Massachusetts Gypsy Moth Commission is Arsenate of Lead, which has been placed 

 on the market in a very convenient form under the name of Bowker's Disparene and of 

 Swift's Arsenate of Lead. The chief advantages of Arsenate of Lead are that it can 

 be applied to all kinds of foliage with less danger of injury than is the case with Paris 

 green ; and, on account of its fine state of division, it lasts longer on the foliage, 

 because it does not wash off so easily. The cost of using it is about the same as that 

 of Paris green, because, although cheaper, pound for pound, it is necessary to use three 

 times the amovmt of it to get the same results. Arsenate of Lead may be made at home. 

 Pormute for its preparation vary slightly; but in the United States Division of Ento- 

 mology, Bulletin No. 41, the following instructions are given for making the Arsenate 

 of Lead wash ready for use : — 



Arsenate of soda 10 ounces. 



Acetate of lead 24 " 



Water 150 to 200 gallons. 



The arsenate of soda and acetate of lead should be dissolved separately and then 

 I ourc'l into a tank containing the required amount of water. These chemicals unite 

 readily, forming a white flocculent precipitate of lead arsenate, which is easily kept in 

 suspension and can be used in excessive strengths on delicate plants without the addi- 

 tion of lime. When sprayed upon the foliage, it forms a filmy adhering coat, which 

 is but little affected by ordinary rains. 



Another formula for making Arsenate of Lead is that recommended by Prof. TI. 

 T. Fernald, and is : 



Arsenate of soda, 50 per cent, strength 4 ounces. 



Acetate of lead 11 " 



Water 150 gallons. 



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