DISEASES OF CULTIVATED PLANTS 405 
the joss of stand on smaller plants is frequently very heavy. Good results in 
prevention have been obtained, both from steaming and from formalin drench 
as per directions in seed and soil treatments. The fungus also attacks the 
succeeding crops of tomatoes, cucumbers, etc. Attention must in all cases first 
(be given to growing healthy seedling plants,to be followed by soil disinfection. 
See Circular No. 57). 
Ls = 
Fig. 56. On the left is shown a healthy lettuce plant, on the right diseased lettuce plant with 
Rosette effects produced by inoculation of pure culture of Rhizoctonia. The effect of the Rosette 
Fungus is shown in destroying absorbent rootlets and in the growth of additional new roots; it als 
prevents the proper development and elongation of the axis or stems of the plant. From Circular No. 57. 
(See also Fig. 57). 
Lettuce Rot or Lettuce Drop. This is by all odds the most troublesome 
disease to the lettuce grower. The plants may rot off at the surface of the 
earth and the central parts, especially of head lettuce, may become attacked by 
the rot fungus (Sclerotinia Libertiana Wm. Fckl.) (Botrytis vulgaris Fr.). The 
fungus appears as a whitened covering with a liberal production of spores in 
clusters. At this Station it has not been possible to succeed with the head 
lettuce because of the rot. Fumigation of house, the use of fresh or steamed 
earth each year and the careful regulation of temperature and water supply, 
seem to be the measures most favorable to prevention. A low night temperature, 
Jess than 50 degrees F. is very desirable, while too higha temperature will 
usually result in disease. Ventilation is all essential ‘during the day. Itis 
desirable also to gather and burn rotted leaves and plants. 
Leaf-Spot. The leaf-spot fungus (Septoria consimilis E. & M.) is frequent 
upon wild lettuce plants and occassionally upon outdoor lettuce, especially in 
late seasons. The small characteristic leaf-spots are not difficult to eee 
from anthracnose. The remedies are confined to avoidance. 
Root-Rot and Stem-Rot. A bacterial stem-blight has been described from 
Vermont, but has not been found with us. A recent stem-rot infection closely 
resembles rosette in the behavior and form of affected plants. Microscopic 
