MARKET DISEASES OF VEGETABLES. 23 



attacks of rot-producing bacteria and fungi. On onions, 

 scald may be followed by slimy soft rot, and large losses 

 were thus incurred in certain shipments from Stockton, Cal., 

 in 1918. Tomato scald opens the way for fungous rots and 

 was an important factor in the losses in Texas and Tennessee 

 shipments in 1918. Sun-scalded muskmelons or water- 

 melons are frequently invaded by saprophytic fungi such as 

 black mold (Sterigmatocystis) and Cladosporium or Alter- 

 naria. Generally these are surface growths more or less 

 confined to the dead tissue. 



Potato scald is discussed elsewhere, as is also sun-scald 

 of bean. 



Because of its predisposition to rot during transit, scalded 

 stock could profitably be culled out before shipment. 



NEMATODE DISEASE. 



OF BEET, CARROT, CELERY, PARSNIP, POTATO, SWEET POTATO, RADISH, 

 RUTABAGA, AND TURNIP 



Cause: A nematode or eelworm (Heterodera radicicola). 



This disease affects the underground parts of plants. It 

 may be recognized on tubers by small, pimple-like swellings 

 or by larger protuberances of the surface, which ordinarily 

 becomes roughened at the infected places. These swellings 

 when some distance apart are circular, but if occurring close 

 together they take on various shapes and sizes. On roots 

 the disease appears as definite galls or knots and conse- 

 quently is commonly called root-knot. 



Eelworm-infected tubers and roots sometimes are con- 

 fused with those affected by other diseases (crown-gall of 

 beets, club-root of crucifers, and "pimply potatoes" due to 

 flea-beetle injury), which also cause a swelling of the dis- 

 eased tissues. The nematode disease, however, may usually 

 be readily distinguished from other maladies by the pres- 

 ence of small, white; pear-shaped nematodes, the adult 

 females, which may barely be seen with the unaided eye 

 when well-infested tissues are broken or teased apart. 



This disease occurs widely in most of the older trucking 

 sections of the southern portions of the United States and 

 in greenhouses everywhere. 



Plants become infected in the field. The disease does not 

 develop or spread in transit or storage. Diseased stock, 

 however, is very subject to invasion by secondary organisms, 

 particularly bacteria. 



Affected stock may largely be eliminated by grading. It 

 never should be shipped, not only because it is unsightly in 

 appearance, of inferior quality, and impaired in market 

 value, but also because it may carry the disease into unin- 

 fested regions. 



Ref. (la). 



ARTICHOKE: GRAY MOLD ROT; BOTRYTIS ROT. 



(See Gray Mold Rot). 



