Cauliflower Diseases 127 



watering unnecessary splashing of soil particles on 

 the plants should be avoided. 



Damping Off 



Caused by Olpidium brassica (Worr.) Dang. 



The symptoms of damping off for cauliflower are 

 similar to those produced by Pythium de Baryanum, 

 p. 17. The sporangia of the parasite may be found 

 singly or in groups in each infected host cell. The 

 zoospores are globose, uniciliate. The resting spores 

 are globose, wrinkled, and star-like in appearance. 



The disease is found mostly in seed beds, where 

 it does considerable damage. For methods of con- 

 trol, see pp. 32-34. 



Downy Mildew 



Caused by Peronospora parasitica (Pers.) De By. 



Symptoms. Downy mildew, while a common field 

 disease, causes considerable damage to young seed- 

 lings in the seed beds. It is characterized by whit- 

 ish downy patches on the underside of the leaf. Seen 

 from above, the affected areas are angular, pale yel- 

 low, and somewhat shrunken. The spots seem to be 

 limited by the veins of the leaves. The disease is 

 common in damp houses. Besides the cauliflower, 

 the radish, and numerous other cruciferous hosts are 

 known to be susceptible to downy mildew. 



The Organism. The sporophores of the fungus 

 are stout and numerously branched, each of these re- 

 peatedly forked. The tips of the smaller branches 



