' CLUB-ROOT ' DISEASE ^6^ 



spores, and destruction of the stumps or remaining parts of the 

 plants is only half a remedy. 



{b) It is important to recognise that all diseased decayed 

 refuse from ' clubbed ' crops constitute a possible source of in- 

 fection, and require to be dealt with accordingly. Whenever 

 practicable, refuse of this character should be burnt ; if thrown 

 away, it should be placed in some situation where it is not 

 likely to be transferred subsequently to cultivated soil, and on 

 no account should it be put on the manure heap. 



Diseased plants should not be given to pigs, for we have met 

 with one or two cases where ground previously free from the 

 disease has been rendered almost useless for the growth of 

 cruciferous crops by the application of manure from pig-styes 

 into Avhich clubbed plants had been thrown. 



(c) It appears that the spores of the organism may remain 

 in the soil dormant though still capable of germination for at 

 least two or three years, or the myxamoebs are able to live as 

 saprophytes for that length of time, for it has been found that 

 healthy plants become infected when transplanted into soil 

 which, two or three years previously, had carried a diseased crop. 

 It is, therefore, advisable to avoid cropping with cruciferous 

 plants for two or three seasons after a bad attack. Crops, such 

 as grain of all kinds, mangels, potatoes, strawberries, and 

 others not belonging to the Crucifers, may be grown without 

 fear of their being injured. 



(i) ' Clubbing ' is rarely or never met with on soils rich in 

 lime, unless plants already suffering from the disease are trans- 

 planted thereon. On the other hand, upon sandy and clay soils 

 which are deficient in this element, ' clubbing' is very often severe. 



The application of a good dressing (3 or 4 tons per acre) of 

 unslacked or recently slacked lime reduces the disease very 

 considerably and frequently destroys it altogether: the lime 

 should be worked into the soil some time before the latter is 

 cropped. 



