670 ADDITIONAL EXERCISES 



carbonate is dissolved, being careful to use no more ammonia than is necessary to 

 complete the solution. Then, after adding the remainder of the required quantity 

 of water, the solution is ready for application. 



Caution. — Plants likely to be injured by Bordeaux mixture are more susceptible 

 to the clear light-blue solution of ammoniacal copper carbonate, which upon drying 

 leaves little or no stain. 



Arsenate of lead is one of the best arsenical insecticides. It has in many cases 

 entirel}- displaced Paris green orchard spra3dng, and there are at least three good 

 reasons for its use. 



First. — The arsenate of lead has great adhesive qualities. It will not wash off 

 even in heavy showers of rain. Some of the experiments at the Alinnesota Experi- 

 ment Station showed the presence of this arsenate on the leaf in sufficient quantity 

 to kill insects, ten weeks after spraying. 



Second. — ^It can be used in any strength without burning the foliage of the plant 

 sprayed, except peach leaves which are burned, if it is too strong. 



Third. — It has some fungicidal properties that are increased when added to lime 

 sulphur. The home-made preparation is made as follows : 



22 ounces acetate of lead (sugar of lead) dissolved in 2 gallons of warm water in 

 a wooden pail. 



8 ounces arsenate of soda dissolved in i gallon water in another wooden pail. 

 These two solutions are poured together and make sufficient quantity of poison for 

 50 gallons of spray. 



Arsenile of Lime. — A home-made preparation much cheaper than Paris green 

 and just as good. It is prepared as follows: 



White arsenic, i pound 1 



Cr3fstal sal soda, 4 pounds \ Stock solution 



Water, i gallon J 



Boil these in an iron kettle for twenty minutes until thoroughly dissolved. The 

 kettle must be kept exclusively for this purpose. The soluble material obtained is 

 arsenite of soda and can be stored away in jugs or bottles, labeled poison, for futiure 

 use. For 40 or 50 gallons of spray, take i J^ to 2 pints of this solution, and 4 pounds 

 of freshly slaked lime. Dilute the lime and stain: then add the stock solution. 

 Pour into the spray barrel, and it is ready for use. 



Bordeaux Mixture. — This is the most valuable fungicide in use for combating 

 plant diseases and consists of a mixture of copper sulphate (blue stone) and stone 

 lime slaked in water. It is used in various strengths. 



Standard Bordeaux Mixtures (Fig. 237) (6-4-50 formula). 



Copper sulphate, 6 pounds. 



Lime, 4 pounds. 



Water to make 50 gallons. 



This mixture can be used successfully on many plants, but on others like the peach 

 and Japanese plum, it injures the foliage. It also sometimes russets the fruit of 

 apples and pears. Tl can be increased in strength for certain purposes bv reducing 



