184 Principles of Plant Culture. 



The arsenical compounds (283) may be added to the 

 Bordeaux mixture, and thus a single treatment will 

 serve for both insects and fungi. 



330. The Diseases Preventable by Bordeaux Mix- 

 ture are the apple and pear scab (328), the downy 

 mildew and black rot* of the grape, the earlyf and 

 late blight$ of the potato, the gooseberry mildew, the 

 leaf-blight of the pear** and some others. 



In all these diseases, however, the treatment is pre- 

 ventive rather than curative. The first application 

 should be made before the disease appears and should 

 be followed occasionally by others as new foliage is 

 formed or as the material is washed off by rains. 



331. Ammoniacal Solution of Copper Carbonate 

 possesses nearly the same fungicidal properties as Bor- 

 deaux mixture, but adheres less strongly to foliage. 

 Being a solution, it requires no straining or stirring, 

 and it leaves less stain on drying than Bordeaux mix- 

 ture, which makes it preferable to the latter for use 

 upon plants of which the fruit is nearly mature. To 

 make this solution, dissolve one and one-half ounces of 

 precipitated copper carbonate in one quart of strong 

 commercial ammonia, and add 25 gallons of water. 

 The ammonia should be procured in a glass or earthen 

 vessel, which should be kept tightly corked. To pre- 

 vent waste of the ammonia by evaporation, prepare im- 

 mediately before spraying. 



332. Potassium-Sulfid Solution is used to some ex- 

 tent to prevent gooseberry mildew (330), and a few 



* Lee stadia Bidwellii. t Macrosporium Solani . } Phytophthora i nfestans, 

 I Sphoerotheca Mors-uvce. ** Entomosporium maculatum. 



