

NOTES ON AND EXPERIMENTS WITH INSECTI- 

 CIDES AND FUNGICIDES IN 1902. 



Chas. D. Woods. 



The year 1902 was not characterized by special abundance of 

 the Colorado potato beetle. Early in the season there were only 

 a few old beetles to be seen on most fields and compared with 

 some years little damage was done by the potato bug even upon 

 potatoes that were inadequately protected. The damage from 

 the flea beetles was not any above and perhaps below that of aver- 

 age years. The insecticides used in the State were practically 

 the same as in past years, Paris green taking the lead. Consid- 

 erable quantities of arsenate of lead and Bug Death were used. 



PARIS GREEN. 



Pure Paris green is aceto-arsenite of copper and should carry 

 58.65 per cent of arsenic. The arsenite of copper with 52.94 per 

 cent of arsenic is sometimes sold under the name of Paris green. 

 As made commercially, there is practically no Paris green which 

 is a strictly aceto-arsenite of copper. Since arsenious oxide 

 (white arsenic) is the cheapest single constituent that enters into 

 the manufacture of Paris green, it follows that the manufacturer 

 will usually endeavor to use as much white arsenic as is con- 

 sistent with making a good green. Forty-five samples of Paris 

 green have been recently examined by the Bureau of Chemistry 

 of the U. S. Department of Agriculture. The total arsenic 

 (arsenious oxide) ranged from 56.2 to 61.2 per cent and the 

 copper (copper oxide) varied from 28.5 to 31.2 per cent. These 

 analyses confirmed our own observation that there are practically 

 no Paris greens on the market deficient in arsenic. 



Since Paris green has begun to be used as an insecticide it has 

 been a familiar experience that sometimes it burns the foliage. 

 The reasons for this have been quite carefully investigated and 

 it has apparently been found that this scorching of the foliage is 

 due to the water soluble arsenic in the goods. In the Paris green 

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