CHAPTER XI 

 SPRAYS AND SPRAYING 



FUNGICIDES are materials used to combat fungi, or 

 small plants which are usually parasitic. 



Bordeaux mixture is the leading fungicide for pota- 

 toes. The ingredients for making this mixture are 

 freshly slaked lime and copper sulphate. The fungi- 

 cidal value lies in the copper compound. The lime is 

 added to .prevent the copper sulphate burning the foli- 

 age, and to make the mixture more adhesive and more 

 readily seen when applied. The amount of lime and 

 copper sulphate used vary considerably. Not less than 

 2 pounds of lime can be used to 3 pounds of copper 

 sulphate. Excess of lime is disadvantageous in some 

 ways, as it renders the mixture less efficient by making 

 it thicker, and in this way more liable to settle 1 and 

 more difficult to apply, causing nozzles to clog, but in 

 a wet season an excess of lime is desirable. A thin 

 mixture can, however, be more uniformly applied. 



Use freshly burnt, clean, firm lime; slake it by pour- 

 ing water, preferably hot, over it in small amounts at 

 a time, until the lime has fallen to a fine powder ; 

 then add enough water to make a thin paste. A 

 large quantity of lime may be slaked at one time and 

 kept covered with water. This is a ' ' stock solution." 



To dissolve copper sulphate, it should be placed in a 



1 (N. Y.) Geneva Bui. 243, p. 320. 

 128 



