94 DISEASES OF CROP-PLANTS 



slowly mixed in, stirring all the time. The remaining water is 

 then added. The solution does not keep well, and should be 

 used fresh. 



According to O. Butler the amount of ammonia indicated is 

 insufficient, and should be increased to i| pints to each ounce of 

 copper carbonate, a stable stock solution being prepared accord- 

 ing to the formula : — 



Copper carbonate ... ... i ounce. 



Strong ammonia ... ... i| pints. 



Water ... ... ... i pint. 



adding water at the rate of 3 gallons to each pint of stock solution 



when required for use. 



Probably the method which will be found to be in many 

 respects the most convenient is that of dissolving the precipitate 

 of Burgundy mixture by adding sufficient ammonia. According 

 to O. Butler the product compares very favourably in efficiency 

 and cheapness with the ammoniacal solution of copper carbonate 

 made according to the ordinary formula. 



Sulphur Fungicides. 



Sulphur. 



Finely divided sulphur is a valuable fungicide for use when 

 action on exposed mycelium is required, as in the case of the 

 powdery mildews (Erysiphaceae). It is applied direct in the 

 form of dust, or is deposited from liquid sprays. 



The dry material has two commercial forms, powdered 

 sulphur or sulphur flour, obtained by grinding, and sublimated 

 sulphur or " flowers of sulphur " deposited from sulphur vapour. 

 The most satisfactory and economical is that which is most 

 finely divided, and both forms vary considerably in this respect. 

 Examination under a lens or sifting through fine gauze enables 

 comparisons of quality to be made. 



The fungicidal action of sulphur depends on fumes of uncertain 

 composition which are given off under the influence of the sun's 

 heat. Its effects are therefore obtained to the fullest extent in 

 warm dry weather. Rain and high winds should as far as 

 possible be avoided, and where this cannot be done, lime-sulphur 

 solution should be used. The applications are most effective in 

 the early stages of development of the fungus. The mixture 

 of an equal quantity of powdered lime with the sulphur, often 

 recommended, was found by F. M. Blodget to neutralize to a very 

 considerable extent its fungicidal action. 



Lime-Sulphur Solution. 



Lime-sulphur solution may be used to replace sulphur where 

 an adhesive spray is preferred to a powder. It has a special 



