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JOURNAL OF ECONO^IIC ENTO^IOLOGY 



{Vol. 8 



The Problem. — Three questions arose regarding the possible re- 

 sults of combining Nicotine Sulphate with Bordeaux Mixture. 



1. Is free copper sulphate released as a result of the combination? 



2. Does the nicotine sulphate decompose in such a combination? 



3. Is the nicotine in the combination precipitated? 



The first question would indicate the bearing of the combination 

 on the production of leaf injury. 



The second and third questions would, perhaps, indicate the modi- 

 fication in the insecticidal properties of the nicotine in the combination. 



Copper Sulphate Not Released. — The 4-4-50 formula was used 

 in making up the Bordeaux for the experiments. The chemical expe- 

 riments were duplicated with commercial Bordeaux paste with results 

 similar to the results recorded below with home-made Bordeaux. A 

 commiercial preparation of Nicotine Sulphate, containing 40 per cent 

 nicotine, v/as used at dilutions of 1 to 800 and 1 to 1000. 



Bordeaux injury on the fruit or foliage is caused by free copper sul- 

 phate. In our experiments we used the potassium ferro-cyanide test 

 for free copper sulphate in the Bordeaux before and after the com- 

 bination with Nicotine Sulphate. The tests were made immediately 

 after combining the two, and one, two and three daj^s later. In none 

 of these cases was free copper sulphate present. To ascertain whether 

 the indicator retained its properties in the combination, some free 

 copper sulphate was added and its presence immediately shown by 

 the dark reaction with the potassium ferro-cyanide. 



No Leaf Injury. — Field tests on a small scale were carried on in 

 which Bordeaux 4-4-50, used alone and in combination with Nicotine 

 Sulphate, 1 to 800, were sprayed upon foliage. These tests were con- 

 ducted on August 16. It is true that foliage-spraying tests carried on 

 so late in the season would not be conclusive in that the same degree 

 of resistance to spray injury does not hold throughout the growing 

 season. However, the plants sprayed included some with tender 

 foliage, and the results may be taken as supplementary to the lab- 

 oratory findings and the records of other workers. The foliage of the 

 following plants was sprayed: Apple, pear, peach, sweet cherry, sour 

 cherry, black walnut, rose, bean, tomato. 



The foliage was examined at intervals of several days — the last 

 examination being m,ade on September 4 — almost three weeks after 

 the first application. 



Another set of foliage on the same species of plants was similarly 

 sprayed on August 22. In neither case did leaf injury result. 



During the period the daily maximum temperature ranged from 

 75° to 94° and the minimum from 61° to 76°. For four days following 

 the first application there was no rain and for two days following the 



