INSECTICIDES AND FUNGICIDES. 31 



2. Bordeaux Mixture with Paris Green, 



These two can be combined safely. The excess Hme in the Bordeaux 

 unites with any free arsenic which may be present in the insecticide, and 

 thus protects the leaves from arsenical injury. Paris green also has fungi- 

 cidal value (43); the combination, therefore, is slightly more beneficial 

 than the fungicide alone. No injurious or neutralizing reaction occurs 

 between the two materials. 



3. Proprietary Copper Preparations. 



]Most of these preparations have the constituents of Bordeaux mixture 

 with the addition of a stomach poison, usually lead arsenate but occasion- 

 ally Paris green. Both are compatible with the fungicide, and the effect 

 should be the same as previously described for combinations of these 

 arsenicals with Bordeaux. 



The tendency of manufacturers of commercial copper mixtures has been 

 to recommend the dilution of their product to a copper content lower than 

 that of 4-4-50 Bordeaux. Within recent years, however, they have been 

 increasing the amount of copper and recommending a more concentrated 

 application. The percentage of arsenic has been more nearly that recom- 

 mended by entomologists for control of insects. Thus when the purchaser 

 has mixed in his spray tank enough of a low-copper preparation to conform 

 to the standard given in Table II, he will have the arsenical in great excess 

 of the amount needed, and therefore is paying a ver}^ high price for his 

 arsenic. 



The manufacturer is required to state on the label the amount of 

 arsenic which is present, either as metallic arsenic or as arsenic or arsenous 

 oxide. As an aid to the purchaser in making dilutions and in estimating 

 the value of the preparation. Table II shows the guaranteed arsenic content 

 and the amount of material required to furnish arsenic equivalent to the 

 standard formula (0.293 pound of metallic arsenic to 50 gallons of water), 



4. Bordeaux Mixture with Lead Arsenate or Calcium Arsenate 

 AND Nicotine Sulfate. 



These materials are compatible and make an efficient combination. 

 Some hesitancy was felt at first in regard to the safety of such a combina- 

 tion, owing to the supposed reaction between copper and tobacco com- 

 pounds, and the possibility of serious burning of foliage by the resulting 

 products (44) . It has been demonstrated, however, by chemical analj^ses 

 and extensive field tests, that there is no objectionable reaction when 

 nicotine in the form of sulfate is combined with Bordeaux mixture; hence 

 this combination may be used (45). 



In preparing this spray the nicotine sulfate should be added just before 

 application, and thorough agitation should be given to insure an even 



