48 PEACH LEAF CUEL: ITS NATURE AND TREATMENT. 



of Bordeaux mixture in the spring, although he adds, as if doubting 

 its utility, that the mycelium of the parasite winters over under the 

 cortex of the branches/ 



In France, in 1895, Prillieux published the first volume of a work 

 on plant diseases, devoting several pages to the consideration of peach 

 leaf curl.*^ In this work the recommendations for treatment appear- 

 ing in his paper in 1872 are not given, but instead it is stated that 

 treatments with the salts of copper seem sometimes to produce good 

 results in preventing the multiplication by spores; but, as in the case 

 of Berlese, he adds, as if in doubt of the value of such treatments, 

 that they are without effect upon the perennial mycelium hidden in the 

 tissues. 



B}^ the year 1898 the true idea of the preventive treatment of curl 

 had been grasped in Germany. Professor Weisz, in his paper on 

 plant diseases,'' published that year, cites the present method of con- 

 trolling curl. After renewing the older recommendations to cut off 

 and burn the affected twigs, he says that the trees should be sprayed 

 with copper-soda or copper-lime solution (eau celeste or Bordeaux 

 mixture), the first time he/ore the buds open. That these recom- 

 mendations are not the results of work done by Weisz, however, 

 appears probable, for his description of the disease is evidently quoted, 

 as he falls into the error of Winter, Frank, Kirchner, and other 

 writers in stating that the bloom produced by the fruiting of the 

 fungus appears upon the under surface of the leaves. Had he worked 

 upon this disease in the field he would not have been apt to follow 

 the above authors in their erroneous description of the fruiting habits 

 of the parasite. 



DEVELOPMENT OF THE PRESENT METHODS OF TREATMENT. 



The successful treatment of peach leaf curl dates from the time 

 when fungicides were first applied to dormant peach trees. So far as 

 learned, this treatment was first practiced in California, being intro- 

 duced by the winter application of sprays for the destruction of the 

 San Jose scale {Aspidiotus pernidosus). This insect was first discov- 

 ered in the Santa Clara Valley about 1870, but some time had elapsed 

 between the date of its introduction and the use of the stronger winter 

 sprays for its control. 



Caustic soda and potash were early tested against this insect, and 

 afterwards sulphur was added, the sulphides of potassium and sodium 

 being used by many growers. Somewhat later whale oil soap and sul- 



1 Berlese, A. N., I Parassiti Vegetali delle Piante Coltivate o Utili, preface dated 

 1894, pp. 124-126. 



-' Prillieux, Ed. , Mai. d. Plantes Agr. , Paris, 1895-97, pp. 394-400. 



=> Weisz, J. E., Die schiidlichsten Krankheiten unserer Feld-, Obst-, Gemuse- und 

 Garten-Gewachse, Miinchen, 1898, p. 45. 



