20 



The one having the most energetic action is found to be some form 

 of soluble copper. In the use of the sulphate it is known that one 

 part of the metal in solution in one million parts of water will suspend 

 entirely the germination and growth of many of these spores. The 

 use of the Bordeaux mixture did not arise out of this knowledge, but 

 the reverse. Bordeaux mixture had a fungicidal effect and investi- 

 gations that followed this formation developed the fungicidal power 

 of copper in solution. 



How then can the effects of the insoluble oxide of copper in the 

 Bordeaux mixture, and that remaining after the evaporation of the 

 water and ammonia of Eau Celeste, as well as the insoluble carbonate, 

 be explained? It is doubtless to be found in a very slight solubility 

 of these substances in the infinitesimal amounts of ammonia and 

 carbonic acid existing in rain water and that of dews.* 



These considera:ions influenced me to try the effect of a soluble 

 salt of copper in the i)lace of, or in comparison with, these insoluble 

 mixtures. After much experimenting I found that no injury arose 

 from the application of a solution of sulphate of copper so weak as 

 one pound to 800 gallons. Twice that strength would produce serious 

 results on peach trees as late as July. It may be that other foliage 

 may suffer at some seasons from the weaker dilution, but many plants 

 will endure the stronger. I have used, the past summer, this solution 

 of one pound to 800 gallons very largely, and in direct comparison 

 with the other preparations of copper. The character of the season 

 has been such that the results are not fully decisive on account of 

 the unexpected, nefirly entire, exemption from fungi. How much of 

 this is due to my preparatory treatment I cannot determine as the 

 checks furnish but little information. There was not a drop of rain 

 and scarcely a sparkle of dew between the 4th and 17th of June, just 

 the time when many of these spores are actively set free. The fungus 

 on the leaf of the horse-chestnut, which has been very prevalent on 

 my grounds for some seven years, did not show a spot. Anthracnose 

 of the young canes of the grape which threatened the life of the vines 



* While this is all very true, the success that has attended the use of the Bordeaux 

 mixture, the fact that there is no danger from its injury to the foliage, and that it adheres 

 80 long to the surface of the leaves and fruit, always ready to give up the little soluble 

 matter it contains to the moisture of dews and rains, makes it the most reliable and 

 effectual fungicide we have thus far found. 



Further experiments in the line suggested are being made by many of the experiment 

 stations, wliich are sure, sooner or later, to formulate the best, safest and most economical 

 fungicides and insecticides for general use, and Dr. Fisher's work the past year is of great 

 value in this direction. 



