DiIsEASES OF VEGETABLES 138385 
such conditions can be avoided but no remedy is known for out- 
door lettuce. The only hope lies in obtaining varieties or strains 
less subject to the disease. 
Rhizoctoma Rot (Corticium vagum B. & C., var. solani Burt.), 
Fig. 892. This is a very destructive disease af outdoor lettuce in 
this state and is of considerable importance in greenhouses. The 
rot begins where the bottom leaves rest on the ground and gradu- 
ally works up into the head, destroying the blades of the leaves 
and usually leaving the midribs and stem more or less intact. 
Under glass, care in watering, so as to keep the leaves and surface 
Fic. 391.— CucuMBER WHITE PICKLE 
of the soil as dry as possible, usually holds the disease in check. 
Outdoors little can be done towards controlling it, but thorough 
drainage and frequent cultivation are of value. In greenhouses 
eoil sterilization, preferably by steaming, insures crops free from 
the disease, but is out of the question for fields on account of cost. 
Botrytis Rot (Botrytis cinerea Pers.). This rot is of no 
importance outdoors but is occasionally destructive under glass. 
Diseased parts are covered with a dirty grey fuzzy mold. The 
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