Definition of black root rot
: any of several diseases of plants marked by dark often confluent lesions of the root and sometimes the crown often involving the whole cortex: such as
a : a disease of apples caused by a fungus (Xylaria mali)
b : a disease of tobacco and various other plants caused by a fungus (Thielaviopsis basicola)
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Merriam-Webster unabridgedWords at Play
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