CHAPTER V 

 Plant Enemies 



There never was a cure like a prevention. As a preventive 

 against insects and diseases avoid localities favorable to disease, 

 burn all affected stock, rotate crops, keep down weeds which har- 

 bor insects or diseases, refrain from planting affected stock and 

 have preventive remedies at hand. 



DISEASES 



"Whenever the normal functions of plants are interfered with, 

 the plant is diseased," says Dr. Freeman of the University of Minne- 

 sota. But many of the garden troubles are not true diseases. Plants 

 become yellow because they are getting too much water or too 

 little, or, perhaps, their roots are affected by some insect, or perhaps 

 the soil is too poor or too rich. Real diseases are caused by certain 

 fungi and germs. They affect parts of plants and may be prevented 

 from spreading, but the affected parts cannot be cured. There is 

 very little real information available for the control of plant diseases; 

 each disease on each plant requires special treatments at special 

 times. The control of plant diseases usually depends upon the use 

 of copper or sulphur in some form. 



FUNGICIDES. The following will be found helpful in con- 

 trolling many of the destructive plant diseases: 



A. Bordeaux Mixture. This is the most effective remedy 

 for many leaf spots and rusts. It discolors the foliage and, there- 

 fore, cannot be used in many cases. The ingredients are, 4 pounds 

 of copper sulphate (blue vitriol), 4 pounds of quick or unslaked 

 lime, and 50 gallons of water. Both the copper sulphate and the 

 hme must be in solution before the two substances are mixed to- 

 gether ; in other words, only dilute solutions must be mixed together, 

 otherwise the mixture will not be proper and will injure the plants. 



For smaller amounts, Peltier gives these directions: "A stock 

 solution of copper sulphate is made by dissolving one pound of 



