146 TOMATO CULTURE 



affected stem is put in a moist chamber made from 

 a covered or inverted dish, there will develop an ex- 

 ceedingly vigorous growth of snow-white fungous my- 

 celium which, after a few days, bears numerous round 

 shot-like bodies, at first light-colored, then becoming 

 smaller and dark-brown. These are the sclerotia or 

 resting bodies of the fungus. This fungus, called 

 Sclerotium sp., or "Rolf's Sclerotium," is noteworthy 

 because it attacks potatoes, squash, cowpea, and a long 

 list of other garden vegetables and ornamental plants. 

 The only satisfactory means of control is rotation of 

 crops, using corn, small grain, and the Iron cowpea, a 

 variety immune to this and other diseases. Suscep- 

 tible crops should be kept from infected fields for two 

 or three years. 



Root-knot (Heterodera radicicola (Greef) Mill.) 

 attacks tomatoes in greenhouses and is in some cases 

 an important factor in southern field culture. It is 

 caused by a parasitic eel worm or nematode, of minute 

 size, which penetrates the roots and induces the for- 

 mation of numerous -irregular swellings or galls, in 

 which are bred great numbers of young worms. The 

 effect on the plant is to check growth and diminish 

 fruitfulness, in advanced cases even resulting in death. 



The remedy in greenhouse culture is thorough soil 

 sterilization. In the open field this is impracticable 

 and recourse must be had to a rotation with immune 

 crops, which will starve out the root-knot. It must now 

 be borne in mind that the root-knot worm can attack 

 cotton, cowpea, okra, melons and a very large number 

 of other plants. The only common crops safe to use 

 in such a rotation in the South are corn, oats, velvet 



