and the yellow dwarf virus. These diseases are all widely distri- 
buted in Louisiana, where most of the crop is grown. 
None of these diseases are adequately controlled. Rotation and 
good cultural practices are of some help against fungus diseases. 
Yellow dwarf virus is carried in the bulbs but not in the seed, 
Therefore, plants grown from seed are not likely to be seriously 
damaged unless grown near plants produced from infected sets or 
grown from bulbs for seed. 
Spinach 
Spinach is severely affected by leaf blight, wilt, and virus di- 
seases. Damping off is damaging to stands of seedling plants, 
Fusarium wilt causes loss in Texas and Virginia. Downy mildew 
damages the leaves and is a major cause of loss, particularly in 
humid coastal areas, White rust is epidemic in Texas, Arkansas, 
end Oklahoma, but has not caused losses elsewhere, The cucumber 
mosaic virus is particularly severe on fall and winter crops. The 
curly top virus causes heavy losses west of the Continental Divide 
and limits preduction in some areas; occasionally the disease ap-= 
pears also in southwestern Texas. 
Damping off can be checked by treating the seed with fungicides. 
The use of resistant varieties has reduced losses from Fusarium 
wilt and cucumber mosaic. No satisfactory control is yet available 
for blue mold, white rust, or curly top. The development of resis- 
tant varieties appears to be the only means of controlling these 
three diseases, 
Sweetpotatees 
Much of the loss of sweetpotatces in the field is due to stem rot 
and wilt. Soil rot is a root disease that stunts the plants and 
causes heavy losses. Less severe losses are caused by black rot 
and scurf. Injury by the rcot-knot nematode and the meadow nematode 
causes considerable reduction in yield and quality. All these di- 
seases occur wherever sweetpotatoes are grown in the United States. 
The loss from wilt cen be reduced by the use of clean seed potatoes 
and clean soil for bedding. Disinfection of the surface of roots 
used for seed also is important. Rotation and the use of clean seed 
stock are the only means of reducing loss from black rot. No adequate 
control measure for soil rot is knomm. Rotation helps to reduce 
nematode injury. 
Tomatoes, for Processing 
Tomatoes in the field are severely affected by wilt diseases, leaf 
spots, fruit rots, virus infection, root-knot nematodes, and non= 
parasitic diseases. 
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