No. 5. DEPARTMENT OF AGRICULTURE. ' 383 



not more than f of 1 per cent, is soluble and the water content not 

 to exceed 50 per cent. The best grades of lead arsenate contain a 

 somewhat higher percentage of active arsenic oxid than provided 

 for in this law, and these pastes are usually in a finely divided phy- 

 sical condition so as to be readily mixed with water and remain in 

 suspension for a considerable time. The arsenate of lead powder is 

 double the strength in arsenic oxid as the paste so that only one- 

 half the amount by weight of powder is necessary to use. If the 

 powder is fine enough to remain in suspension in water, it gives 

 practically the same results as the paste. Otherwise the paste is 

 to be prefen'ed. 



BORDEAUX-ARSENATES 



It is well known, in pest warfare, that very often at the time 

 arsenical sprays are applied to kill insects, certain fungicides also 

 are indicated, and for a number of years it has been the custom with 

 the grower to combine the arsenical with Bordeaux mixture, the 

 most widely used fungicide, thus applying two agents at one opera- 

 tion. The commercial houses were quick to see the advantage of 

 putting on the market a dual purpose spray in concentrated form, 

 accurately compounded, which was ready for use and would require 

 no expert to mix. This has resulted in numerous brands of com- 

 bined insecticides and fungicides sold under various trade names, 

 many of them at exhorbitant prices. The active constituents of all 

 these is none other than arsenate of lead paste and Bordeaux mix- 

 ture paste, the latter of which consists of copper hydrate and calcium 

 sulphate. When manufactured under the supervision of efficient 

 chemists these preparations are ideal for use when a double purpose 

 spray is indicated, especially on potatoes and garden and truck crops 

 generally. 



LIME-SULPHUR SOLUTION 



The lime-sulphur-salt, or so called California wash, was originally 

 developed as a dip for the control of scab on sheep. It was first 

 used as an insecticide on fruit trees in 188G at Fresno, California. 

 In the east the first orchard trees were sprayed with lime-sulphur- 

 salt solution in 1894 with negative results, and it was not until the 

 year 1900 when Prof. Marlett, of the U. S. Bureau of Entomology, 

 used it under favorable weather conditions and secured excellent re- 

 sults. Since that time the use of lime-sulphur washes under various 

 formulae, with and without the salt as an ingredient has spread over 

 the entire United States until now in point of tonnage it exceeds all 

 other insecticides combined. It is recognized as a specific against 

 all scale insects with the exception of the Lecanium scales and is 

 perfectly harmless to trees of all classes during the dormant state. 

 Just as the salt which was originally added to this mixture was 

 eliminated because it lacked insecticidal virtue, so also the excess of 

 lime in the original formulae was reduced to more nearly the quan- 

 tity which would combine with the sulphur in the boiling process 

 in order to reduce the amount of sediment or sludge in the finished 

 product until at the present time the demand among consumers is 

 for a strictly clear filtered solution which will run readily through 



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