202 Bulletin 252. 



V. FUNGICIDES. 



H. H. WHETZEL 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 improtant 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 

 Coi)t>er sulfate P''opo''tion 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 



powder. If small quantities of I'ime are used, hot water is pre- 

 ferred. 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 or 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 pounds required. Dilute this a little by 

 adding water, and strain into the tank. Stir the m-ixture, and add water to 

 make the required 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 is not necessary, and is often impracticable for 

 commercial work, ll 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. 



It is not necessary to weigh the lime in making Bordeaux mix- 



The fcrro- t"''c for <'i simple test can be used to determine when enough of 



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



yellow prussiate of potash in a pint of water and label it 



