246 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Fungicides. 

 Bordeaux Mixture. 

 4 lb. copper sulphate (blue vitriol). 

 4 lb. lime (unslaked). 

 25-50 gallons water. 

 Dissolve the copper in hot or cold water, using a wooden or earthen 

 vessel. Slake the lime in a tub, adding the water cautiously and only 

 in sufficient amount to insure thorough slaking. After thoroughly 

 slaking, more water can be added and stirred in until it has the con- 

 sistency of thick cream. When both are cold pour the lime into the 

 diluted copper solution of required strength, straining it through a fine- 

 mesh sieve or a gunny cloth, and thoroughly mix. 

 The standard mixtures are : 



(a) 25 gallons (full-strength solution, or 4-4-25 formula). 



(b) 50 gallons (half-strength mixture, or 4-4-50 formula). 



It is then ready for use. Considerable trouble has frequently been 

 experienced in preparing the Bordeaux mixture. Care should be taken 

 that the lime is of good quality, and well burned, and has not been air- 

 slaked. Where small amounts of lime are slaked it is advisable to use 

 hot water. The lime should not be allowed to become dry in slaking, 

 neither should it become entirely submerged in water. Lime slakes best 

 when supplied with just enough water to develop a large amount of heat, 

 which renders the process active. If the amount of lime is insufficient, 

 there is a danger of burning tender foliage. In order to obviate that, 

 the mixture can be tested with a knife-blade or with ferrocyanide of 

 potassium (1 oz. to 5 or 6 oz. of water). If the amount of lime is 

 insufficient, copper will be deposited on the knife-blade, while a deep 

 brownish-red colour will be imparted to the mixture when ferrocyanide 

 of potassium is added. Lime should be added until neither reaction 

 occurs. A slight excess of lime, however, is desirable. 



The Bordeaux mixture is best when first prepared. Stock solutions 

 of lime and copper can be made and mixed when required. 



The following, known as the 6-4-50 formula, is in very general use : — 



6 lb. copper sulphate. 



4 lb. lime. 



50 gallons water. 



Bordeaux Mixture for Peach Foliage. 

 The Bordeaux mixture as ordinarily applied frequently injures to 

 some extent the foliage of the Peach &c, causing a shot-hole effect on 

 the leaves. This injurious effect has been shown to be largely obviated 

 by the use of the following : 



3 lb. copper sulphate. 



6 lb. lime. 



50 gallons water. 



This is known as the 3-6-50 formula. Some experimenters have also 

 recommended the following for Peach foliage : 



(a) 2-2-50 formula (Cornell Agr. Exp. Sta., Bull. 180). 



(b) 3-9-50 formula. 



The latter contains three times as much lime as copper sulphate. 



