510 ANNUAL REPORT OF THE Off. Doc. 



PuKiTY OF Materials and Peoper Preparation of Mixtures. 



So far, but one side of the ease has been presented. There \b still 

 another important phase of the subject to discuss before all the fun- 

 damental factors leading to successful spraying results are explain- 

 ed. Part of these factors are beyond the control of the fruit-grower, 

 part are within his control. The purity of the materials used and 

 theii proper preparation and combination are alluded to. These 

 are of as fundamental importance as any of the points already men- 

 tioned. For it is obvious that unless the materials used are pure and 

 up to standard strength, their use cannot lead to successful results, 

 no matter how skilfully and carefully they may be applied. It will 

 be impossible to treat of the scores of materials that have been and 

 are used in spraying operations. Space permits only of the discus- 

 sion of those substances which now constitute by far the bulk of 

 spraying materials in general use. These will be taken up in detail 

 and their necessary qualifications explained.* 



Paris Green. 



This substance, known chemically as the aceto-arsenite of copper, 

 was first used as a remedy for chewing insects about the year 1872,t 

 \^ hen it was recommended for use against the canker worm. A few 

 years later, 1878 or '79, its efficacy against the codling moth was first 

 discovered in Western New York,* Since that time its use as a 

 poison against chewing insects has increased at an enormous rate, 

 until at present many tons are being used for this purpose. 



Paris green wa® first used as a pigment in painting — hence its 

 name. As such its prime quality was its bright green color together 

 with some insolubility in water to prevent it from being washed from 

 painted surfaces by rains. Its chemical composition and proportion 

 of certain chemical ingredients were therefore of secondary import- 

 ance. These considerations, then, did not enter in its manufacture. 

 With its use as a poison spray, however, its chemical composition, 

 together with its insolubility in water, become prime requisites. A 

 demand for a green manufactured solely for its use as an insecticide 

 has been created, which is being met, partly at least, by manu- 

 facturers of the poison. During late years, however, there have 

 been many complaints from users of Paris green both as to its ineffi- 

 cacy and its injurious action upon the foliage of trees. Upon inves- 

 tigation it was found that the greens prepared by different manu- 

 facturers were exceedingly variable in their composition, the results, 



•For further Information regarding the purity of commercial Insecticides and fungicides, see 

 Farmers' Bulletin 146, issued by the U. S. Department of Agrirfilture. 

 tSlingerland, Cornell Univ. Agr. Exp't Station, Bui. 142, p. 50. 



