DISEASES OF CABBAGE 127 



Diseases of Cabbage. — There are several diseases of cabbage 

 which may ]>ecoiii(^ serious where the crop is grown extensively. 

 One of the most prevalent of these is known as the club root, so 

 named on account of the peculiar malformation of the roots of 

 the infected plant. In severe cases this disease so weakens the 

 plant that it does not produce a good head. Spores form in vast 

 numbers in the infected roots and remain in the soil ready to 

 transmit the disease to the succeeding crop. The same disease 

 attacks cauliflower, kale, kohlrabi, turnips and several other 

 members of the mustard family, including weeds, notably the 

 shepherd's purse and hedge mustard. Experiments show that 

 the germs of the disease may remain in the soil for as many as 

 four years following the production of a badly diseased crop, 

 even when no crops subject to the disease are grown upon the 

 land during that time. 



To avoid serious injury from this disease, it is best to prevent 

 the land from ever becoming badly infected with its germs. This 

 can usually be done by practicing a systematic rotation of crops, 

 so that cabbage or any other crop subject to this disease is grown 

 only once in three or four years upon the same land. A slight 

 infection does not seriously damage the crop, and if another crop 

 of the same kind is not grown for three or four years, the disease 

 does not gain much headway. This method of avoiding injury 

 is applicable only to fields which have not become badly infected. 



If it becomes necessary to plant cabbage on a piece of land 

 that has previously produced a badly diseased crop, the stumps, 

 roots and all other refuse from the diseased crop should be re- 

 moved immediately after the harvest, and destroyed by burning 

 or burial. Refuse from a diseased crop should not be thrown upon 

 the compost heap or fed to animals, for it has been found that 

 manure from animals fed upon diseased cabbage or turnips will 

 transmit the disease to otherwise uninfected soil. 



In addition to the removal of the refuse from the preceding 

 crop, a badly infected field should be treated with lime used at 

 the rate of 75 to 150 bushels per acre. The lime is more effective 

 if applied considerably in advance of the setting of the plants. 

 It is usually applied broadcast and allowed to become air-slaked 

 before being plowed under. Then if the land can be replowed 

 before setting the plants, it is an advantage. 



Cabbage plants may become infected in the seed-bed; in fact, 

 they seem more subject to infection while young than after they 



