FUNGICIDES AND THEIR APPLICATION 97 



Some lime is so sluggish that it is necessary to use hot water 

 to start the process and difficult to raise enough heat to complete 

 it, while with hot limes care has to be taken to stop the cooking 

 by adding cold water to prevent the sulphur going into solution . 



Liver of Sulphur. 

 Liver of Sulphur has been used in gardening practice for 

 spraying against mildews and in cases where the deposits left on 

 fruit or foliage by other fungicides have to be avoided. The 

 name in its stricter sense is applied to potassium sulphide, but 

 the commercial substance is a mixture of several compounds. 

 Its fungicidal value depends on its content of sulphides, which 

 varies greatly in different samples. Exposed to air its colour 

 turns from liver brown to greenish yellow, and eventually to 

 grey, and its value is lost. It should be stored in well-sealed 

 tins or bottles, which must be kept full. It is applied at a 

 strength of i oz. to 2-3 gallons of water, but owing to the un- 

 certainty of its composition, and its tendency to burn when used 

 at really fungicidal strengths, its use is not to be recommended. 



A mmonium Sulphide. 



This compound has recently been brought forward as a 

 much more efficient and less injurious fungicide for use against 

 mildews than liver of sulphur. Its preparation can only be 

 undertaken in a chemical laboratory, so that the purchase of 

 commercial stock solution is necessary. Except for ripening 

 fruit or ornamental plants it has no advantage over lime-sulphur. 

 Iron Sulphide. 



This is recommended as a good fungicide non-injurious to 

 fruit. A self-boiled lime-sulphur mixture (see above) is prepared 

 with 10 lb. of lime and 10 lb. of sulphur to 34 gallons of water, 

 and 3 lb. of iron sulphate (copperas) dissolved in 6 gallons of 

 water is added. This gives a black spray. 



Potassium Permanganate. 



A solution of this substance in water is effective against 

 surface mycelium and some spores. It is convenient for use in 

 small quantities on garden plants. J. J. Taubenhaus found that 

 sweet peas could be sprayed with solutions up to 3 per cent, 

 without injury, and that 0.5 per cent, strength was effective 

 against anthracnose. To prepare a i per cent, solution dissolve 

 I ounce in 5 pints of water ; 2 ounces of soap may be added if 

 found advantageous to increase the wetting properties. Potassium 

 permanganate may be added to Bordeaux mixture with a view 

 to increasing the effect against exposed mycelium. 



Spraying. 



Successful and economical spraying depends on the applica- 

 tion of the fluid in such a manner that after drying a thin and 

 even deposit is left on the leaves or other parts of the plant. 

 This can only be secured by a fine mist-like discharge carefully 



