DISEASES OF VEGETABLES 
Proressor J. C. Jaccer 
Assistant Professor of Plant Pathology, University of Rochester, Rochester, 
N.Y. 
CAUSES OF DISEASES 
Diseases of plants result from several 
causes. Unsuitable soil and weather or 
improper cultural methods are often the 
cause of unhealthy plants. Insects are 
more or less injurious to all crops. Many 
diseases result from the growth within af- 
fected plants of minute parasitic plants 
known as fungi and bacteria. Other dis- 
eases, which appear to be of importance in 
New York State to the growers of the 
vegetables treated in this bulletin, are 
briefly discussed. 
METHODS OF CONTROL 
Vegetables can not be cured of disease as can men and animals. 
They must be protected from the attack. The method of control 
to be employed for a given disease is determined by its cause and 
by the nature of the crop attacked. Evidently diseases resulting 
from conditions of soil, weather or culture can be avoided by 
making conditions suitable or by growing crops, varieties or strains 
of plants which are not injured by the conditions. Control meas- 
ures to be employed against the many diseases resulting from 
the attacks of parasitic fungi and bacteria depend primarily on 
the nature and habits of the parasite. 
Crop Rotation. Many parasites live from year to year in the 
soil and will die out and disappear if crops are so rotated that 
susceptible crops are not grown in an infested field for a few 
years. 
Soil Sterilization. Several diseases, resulting from parasitic 
organisms which gain entrance to the plants from the soil, are 
very effectively controlled by soil sterilization. This treatment 1s 
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