150 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



of the subject, have formed the base for much discussion and investi- 

 gation, which it is not necessary to consider here, especially as these 

 chemical changes are variously interpreted by different writers. 

 Those interested in the history and chemistry of Bordeaux mixture 

 may learn of the extensive literature upon these subjects by referring 

 to the writings of Lodeman,^ Fairchild,^ and others. 



In the union of the milk of lime with a solution of copper sulphate 

 there is produced a mixture having great value as a general fungicide, 

 and, as already shown, of especial value for the treatment of peach 

 leaf curl. The mixture possesses several advantages for orchard work 

 over a simple solution of copper sulphate: (1) The addition of suffi- 

 cient milk of lime to a simple solution of copper sulphate neutralizes 

 the acids of the latter to such an extent that the resulting mixture is 

 practically noninjurious to foliage and buds, while still retaining the 

 fungicidal qualities of the simple sulphate solution. (2) The corrosive 

 action of Bordeaux mixture upon pumps, pipes, nozzles, etc., is com- 

 paratively slight. This is of great advantage in doing uniform and 

 thorough work. (3) The lime of Bordeaux mixture causes the spray 

 to become visible upon the trees sprayed, and while this is not 

 desirable in the spraying of maturing fruits, and is avoided by adopt- 

 ing other sprays, it is of very great value in the treatment of bare 

 dormant trees, as it enables the workman to distinguish the sprayed 

 from the unsprayed portions of the tree, and thus to complete his 

 work more thoroughly than could otherwise be done. In case of the 

 employment of hired help for applying sprays, as is usually done, the 

 superintendent or owner of the orchard may know beyond question 

 by the appearance of the trees whether or not his men are doing satis- 

 factory work. As thoroughness is a matter of prime importance in 

 the treatment of peach leaf curl, too much stress can hardly be placed 

 upon this advantage of Bordeaux mixture over several other sprays. 

 (4) The adhesive qualities of Bordeaux mixture are very great, 

 and therefore it is even more desirable for a winter than for a 

 summer spray. This is especially so in portions of the country where 

 the summers are dry, as on the Pacific coast. (5) The whitening of 

 the trees by the use of Bordeaux mixture, provided the spraying 

 is done somewhat early in the winter, is claimed to retard the develop- 

 ment of the buds. The unsprayed trees absorb more heat, which 

 causes the buds to swell during warm days in winter, thus making 

 them liable to injury from subsequent cold.^ 



The methods of preparing Bordeaux mixture for large and small 

 orchards may vary according to the requirements and facilities of the 



^Lodeman, E. G., The Spraying of Plants, Macmillan & Co., 1896. 



'Fairchild, D. G., Bordeaux Mixture as a Fungicide, Bull. No. 6, Division of Vege- 

 table Pathology, U. S. Dept. of Agr. 



» Written, J. C, Winter Protection of the Peach, Mo. Agr. Exp. Sta. Bull. No. 38. 

 Some of the conclusions from the work of Mr. Whitten are: Whitening the twigs and 

 buds by spraying them with whitewash is tlie most promising method of winter pro- 

 tection tried at the Missouri Station; whitened buds remained practically dormant 



