Aster Diseases 209 



parently confined to the foliage, the lower leaves 

 usually becoming infected first, then dry and shrivel. 

 Leaf blight is as yet of no importance in this coun- 

 try. 



Wilt or Stem Rot 



Caused by Fusarium sp. 



Symptoms. This disease appears as soon as the 

 plants are set out and persists throughout the grow- 

 ing season. It is, however, most noticeable during 

 planting time and at blossoming. The trouble usu- 

 ally becomes apparent first on the lower leaves. 

 Here the normal color disappears, turning to a dull 

 yellowish green, followed by wilting. This seems 

 to spread throughout the length of the stem although 

 the disease is usually confined to one side of the 

 plant (fig. 42, c). This gives it a very characteris- 

 tic appearance, since one side of the plant has a 

 dull-green, wilted, blighted appearance and only 

 one half of some of the leaves and flowers are af- 

 fected at first. When pulled up, the roots and stems 

 of a diseased plant appear perfectly healthy. 

 However, if one splits open lengthwise the stem of 

 an infected plant, he will find that the seat of the 

 trouble is localized in the interior of the woody or 

 vascular tissue, the latter of which will be darkened. 

 Infection in this case no doubt takes place in the 

 seed, at the seedling stage. Although some plants are 

 able to make a little headway in spite of the dis- 

 ease they too finally succumb. The cause of the 



