CHAPTER XX 

 Tomato Diseases 



By W. A. ORTON 

 U. S. Department of Agriculture 



DISEASES NOT CAUSED BY FUNGI OR INSECTS 



The health of tomato plants is to a large extent 

 dependent on the conditions under which they are 

 being grown. The character and physical condition 

 of the soil, the supply of water and plant food, the 

 temperature and amount of sunlight, are all factors 

 of the greatest importance in the growth and devel- 

 opment of the crop. When there are variations from 

 the normal in the case of any of these the plant adapts 

 itself to the change as far as possible, but its func- 

 tions may be so disturbed as to result in ill health or 

 disease. It is in many cases difficult to draw a line 

 .between a natural re-action of the plant to its environ- 

 ment and a state of disease. For example, the trouble 

 described in the next paragraph seems to fall into the 

 first class. 



Shedding of blossoms. The tomato is very liable 

 to drop its buds and blossoms and in some instances 

 partial or total crop failures have resulted. The prin- 

 cipal causes are an over-rapid growth, due in many 

 cases to an excess of nitrogenous fertilizers, unfavor- 

 able weather conditions, especially cold winds, contin- 

 ued rainy or moist weather, which hinders pollina- 



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