324 Report of the Horticultural Department of the 



The lime is added only to prevent injury to foliage and to make the 

 mixture more adhesive and more easily seen after being applied to the 

 foliage. Lime water will not do. A very thin white wash made from 

 lime and water, commonly called milk of lime, is needed. The rela- 

 tive amounts of lime and copper sulphate which are used may be 

 greatly varied because a great excess of lime may be used without 

 injury to foliage, but it is absolutely essential that enough lime be 

 used, or injury to foliage will surely follow. It is not safe to use less 

 than two-thirds as much lime by weight as of the undissolved copper 

 sulphate ; that is to say, in the proportion of 2 lbs. of lime to 3 lbs. of 

 copper sulphate. 



Excess of lime. — The question will be asked : Why use any excess 

 of lime ? The reply is that under certain weather conditions an excess 

 of lime tends to prevent injury to the leaves by bordeaux mixture ;^ as 

 it also does when certain arsenical poisons are added to the bordeaux 

 mixture. Fresh interest was given to the question of the best pro- 

 portion of lime to copper sulphate because of the widespread injury 

 to bordeaux-sprayed foliage in 1902. 



Heretofore two pounds of quicklime have been recommended for 

 neutralizing three pounds of copper sulphate ; and this proportion 

 abundantly satisfies the ferrocyanide test. In view of the experience 

 of 1902 it appears that a larger proportion of lime is desirable. 

 Under ordinary circumstances it seems best not to use a greater 

 weight of lime than of copper sulphate since it has been shown that 

 a great excess of the lime tends to render the bordeaux somewhat less 

 efificient against fungi. A thick mixture cannot be sprayed so readily, 

 neither can it be applied so uniformly, as a thinner one. The solid 

 particles do not stay in suspension so well. For instance, in a mixture 

 made according to the normal formula and poured into a glass cylin- 

 der 15 inches high, the solids settle between 3 and 4 inches in one 

 hour. In a similar cylinder containing a mixture made with a large 



^Bulletin No. 220 of this Station, pp. 225-228. 



