112 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



given to the suitability of the soil for Peach-growing and to the selection 

 of efficient stocks &c. * 



Clearly the more suitable the conditions under which Peach cultiva- 

 tion is carried out the less risk there will be of disease, but when disease 

 does appear it is not always easy to determine exactly what conditions 

 are wrong, and until the cause is ascertained it becomes imperative 

 to find some remedial measure to prevent the disfigurement and fall 

 of the leaves and failure of the fruit. 



It was decided to attempt to bring the Exoascus curl under control 

 at Wisley and to try in turn every method that held out any promise 

 of success, and at first to concentrate on the idea of a simple fungicidal 

 wash. Of the mixtures possessing undoubted fungicidal properties, 

 and at the same time efficient and inexpensive, Burgundy mixture was 

 chosen for a test upon the Wisley trees. 



Sulphate of copper is known to be a deadly poison to plant life, 

 and plants vary considerably in their reaction to it. The object of 

 Bordeaux and Burgundy mixtures is to obtain copper in an insoluble 

 and non-poisonous form, and to deposit a film of this copper on the 

 whole surface of the plant. According to various authorities, and 

 more recently Barker and Gimingham, this insoluble copper is then 

 acted upon by excretions from the germinating fungi, which change 

 infinitesimal quantities of the insoluble copper again into soluble 

 copper sulphate, and the latter acts as a poison to the fungus. The 

 fungus, as it were, prepares its own death potion. The quantities of 

 copper sulphate liberated are so small that, if the ingredients of the 

 mixture are present in suitable proportions and in a suitable state of 

 dilution, no harm is done to the plant. 



Clearly the secret of the successful use of Burgundy depends 

 paramountly upon covering the surface of the twig or leaf as uniformly 

 as possible with a fine film of insoluble copper. This object can be 

 attained to a great extent by the proper mixing of the Burgundy 

 mixture itself. The mixture consists of two simple and inexpensive 

 ingredients — copper sulphate (98 per cent, purity) and carbonate of 

 soda. Solutions of these salts are made up in separate wooden 

 vessels. If the salts are ground to a fine powder they will dissolve 

 easily, but if hot or warm water be used the solutions must be allowed 

 to get thoroughly cold before being mixed. The two solutions are then 

 mixed together when as cold as possible, and there is obtained a 

 gelatinous precipitate of copper carbonate (insoluble) suspended in 

 an extremely dilute solution of sodium sulphate, which is itself harmless 

 to the plant and can be removed if necessary. This gelatinous 

 precipitate appears only when the salts are mixed cold ; when warm, 

 the precipitate is of a different character and much less efficient. The 

 gelatinous character of the precipitate gives it its adhesive power. 

 The power of adhesion can be still more increased by the use of a little 

 milk, and experiments in progress* at Wisley foreshadow still greater 

 improvements in the preparation and efficacy of Burgundy mixture. 

 * Gardeners' Chronicle, December 8, 1894, p. 691. 



