Treatment of Pear Scab* in 18o,. 
Experiments in treating pear orchards with a view to prevent- 
ing the injury of the fruit by the fungus which causes pear scab 
were undertaken by the Station Horticulturist in 1894 for the 
purpose of gaining information concerning the following 
questions : | 
1. What is the least number of treatments with Bordeaux mix - 
ture, 1 to 11 formula,’ which will practically prevent injury from 
* Fusicladium pyrinum (Lib.) Fck’l. 
9 With this formula one pound of copper sulphats and the necessary amount of lime are used 
to make 11 gallons of the mixture; this formula may also be expressed as one kilogram of 
copper sulphate and the necessary, amount of lime to make about 110 I'tres of the mixture. 
No simple means of indicating the strength of Bordeaux mixtures has as yet come into 
general use. The expression used above is simple and readily understood. The unit of 
weight by which the amount of copper sulphate is determined is first stated and then the . 
amount of Bordeaux mixture which is made with this amount of copper sulphate is given. 
Thus, “1 to 8 formula’? means that one pound of copper sulphate is us2d in making eight 
gallons of the mixture; ‘'1 to 6 formula”’’ means thit one pouad of copper sulphate is ured in 
making six gallons of the mixture, etc. 
In practical field work the only ingredient of Bordeaux mixture that must be accurately 
weighed is the copper sulphate. The necessary amount of lime is readily determined by means 
of the potassium ferrocyanide test. The simplest way, therefore, to express the strength of 
different formule is, as just stated, by giving first the unit of weight of copper sulphate and 
then the measure of the mixture which is made from the given amount of copper sulphate. 
In recent publications of the United States Department of Agriculture, the strength of differ- 
ent formu’ss for the Bordeaux mixture is expressed in terms of the formula first used exten- 
sively in the work of that Department, namely, ‘‘six pounds of copper sulphate, four pounds 
of lime and 22 gallons of water,’’ which is cet up as a standard formula to which all others are 
referred. In this case six pounds of copper sulphate are taken as a unit of measure in terms 
of which various other formu’ are to be expressed. According to this plan a ‘‘60-gallon 
‘formula’ means that six pounds of copper sulphate are used in making 60 gallons of Bordeaux 
mixture. Would not “the 1 to 10 formula” be a more simple expression for the same thing ? 
The use of Bordeaux mixture is spreading rapidJy among farmers and fruit-growers, who 
know nothing of the “six pounds of copper sulphate, four pounds of lime, for 22 gallons of 
mixture” formula thus arbitrarily selected as ‘‘standard’’ to which all other formu! are to 
be referred. Such terms as “a 60-gallon formula’ may be readily understood by those who 
are quite familiar with the history of the use of the Bordeaux mixture in America, but to the 
vast majority of users of the mixture who are not posted as to the terms of the ‘standard’, 
formula such an expression must be quite confusing, especially since the ‘‘standard”’ formula 
is now little used in practical work. For these reasons it seems desirable in referring to various 
formulee for the Bordeaux mixture to state first the unit of weight in determining the quantity 
of copper sulphate to be used and then state the amount of Bordeaux mixture which is nado 
with this’ amount of ccpper sulphate. 
82 
