136 



Diseases of Economic Plants 



was not known until 1906 or 1907. It chiefly affects the 

 fruit after it has been packed and shipped to market, al- 

 though the infection takes place in the orchard or packing- 

 house, where the disease is largely disseminated by the fruit 

 washers. 



The rot has a peculiar characteristic rancid, penetrating 

 odor, and its presence is further indicated by the prevalence 



Fig. 70. 



Brown-rot of lemons, showing white growth of the 

 fungus. After R. E. Smith. 



of small flies in boxes where there is diseased fruit. One 

 affected fruit in a box communicates disease to the whole. 



Brown-rot is found in nearly pure condition on the fruit in 

 the orchard, especially on fallen fruit or on fruit hanging low 

 on the tree. It is most prevalent in wet weather or on low 

 ground after irrigation. The fungus is visible to the eye in 

 the packing-house, as a mass of white filaments. It is spread 

 by contact alone. 



Orchard infection can be controlled by the use of a heavy 

 mulch under the trees, either straw or a heavy cover crop. 



