286 



VEGETABLE GARDENING 



367. Club root (Plasmodiophora brassicae), also known 

 as "club foot" and "clump foot," is unquestionably the 

 most serious disease of crucifers. (Figure 72.) If un- 

 controlled it will soon spread through a community and 

 render the profitable cultivation of cabbage and allied 

 plants impossible for several years, a situation that 

 has developed in a few sections of the United States. 

 The malady has been known in Europe for more than a 

 century and in this country for many years. 



The disease is most destruc- 

 tive to cabbage and turnip, but 

 also affects cauliflower, brussels 

 sprouts, kale, radish, kohl-rabi, 

 rutabaga, white mustard and 

 many cruciferous weeds, shep^ 

 herd's purse and hedge mustard 

 being especially subject to in- 

 fection. 



The character of the disease 

 and its relation to "clubbing" 

 were determined by the Russian 

 botanist, Woronin, who found 

 that the micro-organism which 

 causes the distorted enlarge- 

 ment of roots was a slime mold 

 and not a bacterium nor a fun- 

 gus. There is distinct "club- 

 bing" in many cases, while in others irregular knots are 

 formed. When the disease has advanced for several 

 weeks, the deformed roots are incapable of supplying the 

 plants with sufficient moisture and nourishment. The 

 plants then become dwarfed and lighter in color. 

 Affected plants wilt quickly in warm, sunny weather, 

 especially if preceded by humid growing weather. The 

 disease is less serious with the early than with the late 

 crop, for with the best conditions for growth at this 



FIG. 



72. CLUB ROOT OF 

 CABBAGE 



