Family Chenopodiaceae 129 



a damping off of the young seedlings, and on older 

 plants a rotting of the crown. In pulling out an 

 infested plant, we find that the outer leaves are dead 

 and dry, while the inner ones are somewhat curled. 

 The roots of such plants invariably are rotted at the 

 crown, the rot generally working inwards to a con- 

 siderable extent. The peculiarity of this disease is 

 that the lower half of the root is generally sound. 

 Frequently the rotted crowns are also found to be 

 cracked at various places. Beets thus affected are 

 worthless for the market. This condition naturally 

 indicates a sick condition of the soil, due to the pres- 

 ence of Rhizoctonia solani. For a description of the 

 fungus see p. 45. 



Control. There are no methods of control known. 

 The factors which favor the trouble are poor drain- 

 age, an excess of soil moisture, and lack of sufficient 

 aeration. Every step taken to overcome these will 

 in a degree help to control the rot. 



Root Knot 



Caused by Heterodera radicicola (Greef) Miiller. 



This disease is different from crown gall or tuber- 

 culosis. Although the symptoms are sometimes 

 manifested as knots or outgrowths on the main 

 roots, usually the knots are found at the tip end 

 of the roots, thereby leaving unmolested the main 

 root. The effect of this disease, however, is to re- 

 duce the size of the marketable beet. Affected 



