258 ItEl'ORT OF OFFICE OF EXPEKIMENT STATIONS. 



In California." whoiv nuniorous oxporinionts were made for this 

 purpose, it was found that the samples of Paris jjreen offered for sale 

 in the niai'kets of that State arc ini])r()vin<r in (juaiity durin«; recent 

 years and that a lai-fre pcrccnta<rc of samples contain less than 4 i)er 

 cent of white arsenic. The number of samjiles which did not con- 

 form to the law. however, indicate that there is considerable room for 

 improvement as compared with Paris <;reen analyses by various 

 eastern stations where nearly all of the samples were found to be sat- 

 isfactory. Adulteration of Paris green is apparently not accom- 

 plished in California by the addition of make-weight materials such 

 as marble dust, gypsum, or barium carbonate. Analyses of various 

 commercial substitutes of Paris green in California showed that 

 most of these materials were highly objectionable on account of water- 

 soluble arsenic compounds in them. On this account they were not 

 recommended since, even if safe, they possess little advantage over 

 Paris green. Wherever the quality of available Paris green is not 

 completely satisfactory it is recommended that arsenate or arsenite 

 of lead and arsenite of calcium be used in place of Paris green. These 

 materials arc comparatively inexpensive and safe to use and may be 

 made at home. 



» The majority of experiments carried on b}^ the experiment sta- 

 tions with Paris green have been concerned with the extermination 

 of some specific insect, as, for example, the codling moth. Some of 

 these experiments will be discussed under the head of the insect 

 concerned. 



At the Xew York State Station '^ experiments were made to deter- 

 mine the effect of certain arsenical sj^raj'S upon the foliage of potatoes. 

 Paris green was applied to poiatoes four times during the season by 

 three different methods in common use, namely, with water, lime- 

 water, and Bordeaux mixture. For the purjDose of comparison other 

 rows of potatoes were treated at the same time with Bordeaux 

 mixture alone, while still other rows were left untreated. Paris green 

 even when applied at the rate of 4^ pounds per acre j:)roduced no 

 injury on the foliage of potatoes at any time during the experiment. 

 The rows which were treated with Paris green in water or in lime- 

 water showed a much more perfect foliage during the season than 

 did the check rows. This difference is apparently due in part to the 

 prevention of late blight of potatoes. Paris green was found to pos- 

 sess considerable value as a fungicide, it being estimated from these 

 experiments that it is one-third as effective as Bordeaux mixture for 

 this purpose. Potatoes treated with Paris green yielded 40 bushels 

 per acre more than the check rows. The potatoes receiving Paris 



California Sta. Bui. 151. & New Yorli State Sta. Bui. 267. 



