174 MAINE AGRicui^TURAL e;xppe;riment station. 1909. 



be seen later this latter recommendation is not in accordance 

 with the most common practice where spraying operations are 

 suspended much too early in the season. 



prope;rIvY made bordeaux essential. 



In attempting to point out the factors which have been found 

 to be responsible for most of the failures to secure complete 

 protection from late blight and rot by spraying with bordeaux 

 mixture, the methods of preparing the mixture, which are com- 

 monly practiced, will first be considered. Unfortunately lack 

 of ability to implicitly follow directions is a common fault of 

 humanity and the maker of spray mixtures is no exception to 

 the rule. 



Bordeaux mixture as now recommended is the result of over 

 20 years of investigation and ex-perimentation by some of the 

 most careful workers in this country and in Europe and the 

 formula recommended for potatoes conforms to the general 

 consensus of opinion among these, investigators. Anyone who 

 departs from the formula, or who does not follow carefully the 

 directions for preparing the spray should bear in mind that he 

 alone is responsible if his bordeaux mixture fails to keep off 

 the disease on account of being too dilute or, if unproperly 

 prepared kills the foliage of the potato itself. 



A rather surprising state of affairs was discovered when the 

 methods of making of bordeaux mixture by potato growers in 

 Aroostook county was investigated. The amount of copper 

 sulphate used for each 50 gallons of spray varied from 2 1-2 

 to 12 or 15 pounds. Very commonly indeed, with a desire to 

 do more efficient work, the amount of copper sulphate is 

 increased to 8 and 10 pounds to 50 gallons of spray without any 

 attempt made to more thoroughly cover the foliage by means of 

 more nozzles per row or better adjustments of the nozzles on 

 the sprayers. Fortunately the potato plant is much less sus- 

 ceptible to such strong sprays than fruit trees which would be 

 ruined by such treatment. 



It is a common practice, also, to use much more lime than 

 copper sulphate — the maker reasoning that lime is inexpensive 

 and a considerable excess may do good and certainly will do 

 no harm. The function of the lime is to unite with the copper 

 sulphate and convert it into temporarily insoluble compounds, 



