DISEASES OF CULTIVATED PLANTS 



AND TREES 



INTRODUCTION 



Some people are fully convinced in their own mind that 

 diseases of cultivated plants increase in number and intensity 

 year by year. In connection with this question it is im- 

 portant to remember that at the present day the majority 

 of persons occupied in the cultivation of plants have learned 

 to attribute every disease to some specific cause generally 

 a fungus or an insect ; something that can be prevented, 

 hence a disease. In bygone times the same amount of 

 injury was considered as a 'visitation,' or due to 'blight,' or 

 some equally indeterminable agency, and was accepted with 

 calm resignation, and not counted as a disease. Cultivators 

 have yet to learn that in addition to epidemics, primarily due 

 to insects or fungi, of which there are admittedly many, 

 numerous diseases of considerable importance are primarily 

 due to physiological causes bad cultivation ; that system 

 of horticultural gambling represented by an atmosphere 

 saturated with moisture and an abnormally high temperature, 

 which results too often in a general break-down of the 

 constitution of plants subjected to such treatment. Such a 

 constitutional weakening invites the attacks of fungi, which 

 promptly complete, but do not originate, the calamity. 

 Growers of tomatoes, cucumbers, etc., have not yet realised 

 that there is a limit to the endurance of plants grown under 

 highly abnormal conditions, and until they do so, they will 

 be the greatest sufferers, as preventive measures under such 

 conditions are, I believe, impossible. It is a pure specula- 

 tion, yet judging from a somewhat extensive experience, is 

 sufficiently often a success to justify its continuance. 



As to whether plant diseases are more prevalent at the 



A 



