Ir] Potato Disease and Allied Diseases 29 
early, and to repeat about three weeks later. Further 
applications are desirable if the unfavourable conditions 
continue. The result of spraying is usually a consider- 
able increase per acre as the plants remain green longer 
and consequently the tubers grow longer. This delays 
the lifting which in some cases may be a disadvantage. 
In dry seasons when the disease does little damage 
spraying may not increase the yield, but as the 
weather is so uncertain it is an insurance to the farmer 
that he will benefit considerably if the disease does 
appear. Early varieties are often dug before the 
disease appears and the advantage of spraying is not 
so marked with second earlies as with maincrop potatoes. 
Burgundy mixture is often used for spraying 
potatoes because although not so good as Bordeaux 
mixture it is much easier to make. It consists of 6 lbs. 
of copper sulphate and 8lbs. of pure washing soda 
dissolved in 50 gallons of water. 
The copper sulphate and the crushed soda are 
dissolved separately and then stirred into the 50 gallons 
of water. 
Dry spraying consists in applying the fungicide in 
the form of a powder and has been successful in 
increasing the yield of potatoes in disease years. It 
is not however as good as Bordeaux or Burgundy 
mixture but it may be safer. Bordeaux mixture 
requires a certain amount of care in making. In the 
hands of an ordinary workman it may prove disastrous 
and scorch the haulm. In cases where the men cannot 
be relied on to make it properly it is better to use 
Burgundy mixture; but with this also they may often 
leave some of the soda undissolved, in which case it is 
safer to use a dry spray. 
