1892.] PUBLIC DOCUMENT — No. 33. 241 



Adam Weaber and Son, Vineland, N. J. ; Rumsey & Co., 

 Seneca Falls, N. Y. ; Field Force Pump Company, Lock- 

 port, N. Y., or W. & B. Douglas, Middletown, Conn. 



When to Apply. — As has been said, this question is of 

 the first importance in dealing with any disease, but the 

 answer varies with the case in hand. In general, however, 

 let it be remembered that all treatment is preventive, that 

 plants once attacked are lost, and that spraying must there- 

 fore be prompt and early. In the case of a disease of an 

 herbaceous crop like potatoes, the first spraying should be 

 given at once on the appearance of the disease in any part 

 of the field or a neighboring field. The same applies to 

 diseases of woody plants which have previously been free 

 from disease ; but where grapes or apples, for instance, were 

 attacked last year, treatment should begin with the beginning 

 of growth, and should proceed on the assumption that the 

 disease will reappear if not prevented. In any case, after 

 spraying is begun it must be repeated until danger is past, — 

 a very variable period, — at intervals which may average ten 

 days or two weeks, but will vary according to circumstances, 

 depending especially on the amount of rainfall, which washes 

 the copper salts from the plants and renders a new applica- 

 tion necessary. It is always best to leave an occasional 

 plant or row of plants untreated among the treated ones to 

 furnish a basis for judgment as to the efficacy of the treat- 

 ment. 



Quantities Needed. — It is very difficult to give any state- 

 ment of the amount of a fungicide required to properly spray 

 any of the various plants on which it may be used. 



The size and leaf surface of plants of the same kind vary 

 so much with their age, the conditions of cultivation, and 

 other controlling factors, that it is hardly possible to say 

 what is an average plant of any sort. Besides this, very 

 few experimenters have published statements as to the 

 quantities used in their work. Yet one of the first questions 

 asked by a beginner is, " How much do I need?" 



With these facts understood, the following figures may be 

 given as approximate statements of the amount of a prepa- 

 ration required for properly spraying the crops named, when 

 a suitable and economical nozzle is used. For another plant 



