136 THE AMERICAN APPLE ORCHARD 



the coi)pcr sulphate. A solution of potassium ferro- 

 cyanide (yellow prussiate of potash) is made by dis- 

 solving- say I ounce of the ferro-cyanide in 6 ounces 

 of water. A few drops of this solution may be 

 dropped into the bordeaux mixture to be tested, when, 

 if the copper sulphate has not been neutralized, it will 

 instantly give a deep brownish-red color. If the mix- 

 ture is properly neutralized no color will appear. This 

 test is very accurate and reliable, provided the bor- 

 deaux is evenly mixed ; but it is too much bother for 

 practical use in the field. 



Even with the greatest care in making and apply- 

 ing bordeaux there sometimes results considerable 

 damage to fruit and foliage from the action of the 

 spray mixture itself. This damage is usually most 

 conspicuous on the fruit, and appears in the form 

 of russety patches or rings. The weather evidently 

 has a good deal to do with the amount of injury, but 

 on the whole this trouble is not very well understood. 

 On account of it careful growers and experimenters 

 now generally use a more dilute bordeaux mixture 

 than formerly. The formula already given is weaker 

 than sometimes recommended, but it may be still fur- 

 ther diluted if any ill efifects are seen. In case of 

 bordeaux injury it will be best to substitute the fol- 

 lowing formula : 



3 pounds copper sulphate 



4 pounds lime 

 50 gallons water 



COPPER SULPHATE SOLUTION 



In early spring before the buds open a thorough 

 spraying with a strong fungicide gives very great 

 returns. Indeed this is probably the most profitable 



