.362 

 V. FUNGICIDES. 



H. H. WHBTZEL AND C. S. WILSON. 



The most important fungicides are as follows: Bordeaux mixture, 

 ammoniacal copper carbonate, potassium sulfide, copper sulfate, flowers 

 of sulfur, corrosive sublimate, formalin, lime-and-sulfur wash. 

 Copper sulfate, 5 lbs. 

 Bordeaux Stone lime or quicklime (unslaked), 5 lbs. 

 mixture. Water, 50 gals. 



Bordeaux is the most important fungicide for general use. The 

 strength varies according to the plant to be sprayed. The formula given above 

 is the strength usually recommended. When a different strength is necessary, 

 the formula is given under that disease. Stock mixtures of copper sulfate and 

 lime are desirable. They are prepared in the following manner: 



Dissolve the required amount of copper sulfate in water in the 



^ jr . proportion of one pound to one gallon several hours before the 



"^ ' solution is needed, suspend the copper sulfate crystals in a sack 



near the top of the water. A solution of copper sulfate is heavier 



than water. As soon, then, as the crystals begin to dissolve the solution will sink, 



bringing water again in contact with the crystals. In this way, the crystals will 



dissolve much sooner than if placed in the bottom of the barrel of water. In case 



large quantities of stock solution are needed, two pounds of copper sulfate may be 



dissolved in one gallon of water. 



Slake the required amount of lime in a tub or trough. Add the 

 Lime. water slowly at first, so that the lime crumbles into a fine pow^der. 



If small quantities of lime are used, hot water is preferred. 

 When completely slaked, or entirely powdered add more water. When the lime 

 has slaked sufficiently, add water to bring it to a thick milk, or to a certain number 

 of gallons. The amount required for each tank of spray mixture can be secured 

 approximately from this stock mixture which should not be allowed to dry out. 



Take 5 gallons of stock solution of copper sulfate for every fifty 



To make gallons of Bordeaux required. Pour this into the tank. Add 



Bordeaux. water until the tank is about two-thirds full. From the stock 



lime mixture take the required amount. Knowing the number 



of pounds of lime in the stock mixture and the volume of that mixture, one can take 



out approximately the number of poimds required. Dilute this a little by adding 



water, and strain^into the tank. Stir the mixture, and add water to make the re- ■ 



quired amount. Experiment stations often recommend the diluting of both the 



copper sulfate solution and the lime mixture to one half the required amount before 



pouring together. This} s not necessary, and is often impracticable for commercial 



work. It is preferable to dilute the copper sulfate solution Never pour together 



the strong stock mixtures and dilute afterward. Bordeaux mixture of other 



strengths as recommended is made in the same way, except that the amounts of 



copper sulfate and lime are varied according to the requirements. 



, 1* is not necessary to weigh the lime in making Bordeaux mix- 



1 he ferro- ture for a simple test can be used to determine when enough of 



cyanide test, a stock lime mixture has been added. Dissolve an ounce of 



yellow prussiate of potash in a pint of water and label it "poison." 



