PREPARATION OF FUNGICIDES 113 



Fungicides. — These are plant poisons diluted to such 

 an extent that they are inimical to the thick-waUed 

 tissues of the host-plants, but are nevertheless sufficiently 

 strong to destroy the tender fungus-tissues. It is therefore 

 apparent that their application can have no efEect upon 

 the mycelium within the tissues of the host-plant. 



It has been already pointed out that several of the most 

 pernicious fungus parasites of cocoa can be held in check 

 by spraying the tree with suitable fungicides. 



The following have been therefore selected from those 

 which have given the best results in the treatment of 

 these pests. 



Bordeaux Mixture. — This is one of the most efficient 

 fungicides, and is probably more largely employed than 

 any other. It may be prepared in the following manner : 



Weigh 20 lb. of copper sulphate, and immerse this, 

 tied up in a piece of sacking, in 80 gallons of water. 

 Slake 15 lb. lime ; add water in small quantities and stir 

 until a perfectly smooth paste is obtained; then add 

 sufficient water to make 80 gallons of lime water. Thor- 

 oughly stir this, and when it is cool slowly mix it with 

 the water in which the copper sulphate was dissolved. 

 It is advisable to prepare the mixture on the same day 

 it is required and not to use iron or tin vessels, as the 

 copper sulphate corrodes these metals. The mixture, 

 after being carefully strained, is ready for use. 



Ammonia and Copper Carbonate Mixture. — Take 1 lb. of 

 carbonate of copper and mix this with 51b. of carbonate of 

 ammonia, and thoroughly dissolve the mixture in hot 

 water. This forms the stock solution, which, previous 

 to application, should be diluted by adding sufficient 

 cold water to make 256 gallons. 



Potassium Sulphide Solution.— Mix potassium sulphide, 

 i.e. " liver of sulphur," in the proportion of 1 lb. to every 

 4 gallons of hot water to form the stock solution. This 

 must be made up to 36 gallons, by adding cold water, 

 before being applied. 



Each of these three mixtures should be applied with 

 sprays fitted with nozzles which distribute the solution 

 in the form of a fine mist. 



