knot nematodes. Verticillium wilt causes some loss in northern 
sections. 
Fruit rot can be controlled by seed treatment, rotation, or the 
use of resistant varieties. Rotation is the only means of con= 
trolling the other diseases, 
Escarole 
The diseases causing loss of escarole are damping off, leaf de- 
cay, alternaria leaf spot, the leaf rot known as drop, and the 
yellowing and dwarfing caused by the aster yellows virus. The 
root-knot nematode causes some damage. All these diseases occur 
in Florida, where the crop is grown almost exclusively. 
Damping off is controlled by chemical seed treatment and seedbded 
sterilization. Leaf disease losses and injury from root-knot 
nematodes can be reduced by crop rotation, The use of insecticides 
to destroy the insect vectors is the only means of control for aster 
yellows. 
Kale 
Disease losses of kaie are caused mainly by clubroot, black rot, 
Fusarium yellows, and mosaic. All these diseases injure the edible 
leaves and stunt the plants wherever the crop is grow. 
The only control for clubroot consists in using clean seedbed 
soil and growing the crop on clean land, although keeping the soil 
alkaline helps. Hot-water treatment of seed and crop rotation re- 
duce losses from black rot. Rotation is the only means of avoiding 
loss from Fusarium yellows, as we have no resistant varieties of 
kale. No control for mosaic is known except isolation of the crop 
from sources of the virus. 
Lettuce, Field-Grown 
Field-grown lettuce is damaged rather severely by tipburn, a non- 
parasitic disease that causes a blackening of the leaf margins and 
discoloration of the large veins. Stunting of the plants by virus 
diseases, chiefly mosaic and aster yellows, is another cause of 
serious loss. Bottom rot and drop causes decay of the stems and 
leaves. Downy mildew causes a withering of tna leaves but no rot. 
The root-knot nematode causes loss in warm regions. 
Tipburn occurs wherever lettuce is grom. Mosaic is widespread, 
but aster yellows is damaging chiefly in the Northeastern States, 
Bottom rot and drop cccur in most lettuce-growing areas, but drop 
is the more common. 
Tipburn is a result of high-temperature injury to rapidly growing 
plants, and the only control seems to be the development of resistant 
Sy 
