TriK Control of Insfxt Pests and Plant Dlseasks. 613 



formula given above is the strwigth usually recommended. When a different 

 strength is necessary, the formula is given under the 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 

 Copper-suljate. 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 watei 

 again in contact with the crystals. In this way, the crystals will dissolve muct 

 sooner than if placed in the bottom of the barrel of water. In case large quanti- 

 ties 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 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. 

 Hydrated or prepared lime of good quality may be substituted for the stone lime. 

 Place the required amount in the barrel or tank and add water. No slaking is 

 required. Do not used air-slaked lime. 



Take five gallons of stock solution of copper sulfate for every 



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



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



lime mixture add the required amount. Stir the mixture, add 



water to make 50 gaMons. 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. 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. 



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



The 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." 



Cut a V-shaped slit in one side of the cork so that the liquid may be poured out in 



drops. Add the lime mixture to the diluted copper sulfate solution until the 



ferro-cyanide test solution will not turn brown when dropped from the bottle into 



the mixture. It is always best to add a slight excess of lime. 



Some plants are injured by the ordinary strength of Borde?ux 

 Bordeaux even when properly made. Others, as the apple, are sometimes 

 Injury. injured by a weak Bordeaux under certain weather conditions. 



Fig. 222. The leaves of most varieties of stone fruits, especially peaches 

 and Japanese plums, are almost sure to be injured by Bordeaux 

 except in very weak mixtures. The injury to these plants consists usually of 

 small holes in the leaves, very similar in appearance to the shot-hole effect of cer- 

 tain fungi. The injury on apple occurs on both the leaves and the fruit. On the 



