varieties. Mosaic is seed-transmitted, and losses could be reduced 
if growers could obtain mosaic-free seed. Rotation is of some value 
in reducing losses from bottom rot, drop, and nematode injury. 
Melons 
Losses in honeydew and honeyball melons are dus largely to damage 
of the leaves by powdery mildew and stunting of the plants and re- 
duced yields from infection by the cucumber mosaic virus and the 
squash virus. Recently there also have been losses from a disorder 
of unknown cause called crom blight. All these diseases are present 
in both Arizona and California, where nearly all the crop is grown. 
Powdery mildew can be partially controlled with fungicides, but 
no satisfactory method has been developed for either mildew or the 
virus diseases. 
Onions 
Disease losses in onions are due chiefly to fungi that cause injury 
to the leaves or roots or decay of the bulbs. The smut fungus at- 
tacks seedlings and causes elongated black blisters on the leaves, 
Most of these plants die. On older plants there is killing of the 
leaves by downy mildew and purple blotch. Pink root kills many of 
the roots and reduces the size of the bulbs. Bulb rots in the field 
include Fusarium rot and white rot. 
Onions are grown under many climatic conditions. Environment affects 
the development and spread of parasitic fungi, and the importance of 
some diseases varies with the region where the crop is grown, Smut 
is important only in the Northern States. Downy mildew is widespread 
but severe chiefly in California, Oregon, New York, and Michigan. 
Pink root is severe in the lower Sacramento and San Joaquin Valleys 
of California, in the Rio Grande Valley of Texas, and on muck soils 
of New York, Ohio, Indiana, and Michigan. Purple blotch and Fusarium 
rot are widespread. White rot is damaging in Louisiana and has been 
reported in Oregon, Kentucky, and Virginia. 
Smut can be controlled by applying formaldehyde in the row as seed 
is planted and by applying chemicals to the seed. No satisfactory 
control has been developed for downy mildew or purple blotch. losses 
from Fusarium rot and pink root can be reduced by crop rotation. 
Peas, Green 
The greatest loss in green peas is due to the various rcot-rot 
diseases, 211 general in occurrence except for southern wilt, which 
is restricted mostly to the South. Serious losses are caused also 
by the widespread ascochyta and bacterial blights. Powdery mildew 
causes some loss where climatic conditions favor it, chiefly in 
semiarid sections in the Rocky Mountain States. Fusariim wilt is 
Tees 
