254 



REMEDIES 



are still commonly attacked, they do not appear to suffer 

 appreciably. 



Artificial control of fungal diseases is accomplished by diverse 

 means, but in each case success depends upon a knowledge of 

 the life-history of the parasite. The method of treatment varies 

 according as the parasite attacks the overground or underground 

 organs of the host. Several of the Fungi considered in the last 



chapter (e.g. Potato Blight) 

 afford instances of the 

 former mode of attack. 

 Diseases of the subter- 

 ranean parts are exempli- 

 fied by the pernicious Wart 

 Disease of the Potato, due 

 to a lowly Fungus of a 

 peculiar kind, and that 

 known as Finger and Toe 

 (Fig. 135 and p. 251), which 

 attacks Turnips, Cabbages, 

 etc., causing irregular 

 swellings upon the root- 

 system. 



One of the remedies 

 most commonly employed 

 against Fungi infesting the 

 overground parts is spray- 

 ing with a fungicide which, 



while deleterious to the 

 FIG. 135. Brussels Sprouts attacked -,1 ,1 i 



by "Finger and Toe" (Plasmodio- P arasi te, leaves the host 

 phora brassica.) [Photo: E. J. S.] practically unharmed. For 



this purpose Bordeaux 



mixture, consisting of a solution of copper sulphate and slaked 

 lime, is one of the most popular. Where the disease is subter- 

 ranean, application of unslaked lime is often successful, as, for 

 instance, in the case of Finger and Toe. Such diseases are, 

 however, far more difficult to eradicate than those which 

 develop overground. They are often best counteracted by 

 growing only such crops, in the infected soil, for several seasons 

 in succession, as are not attacked by the parasite in question. 



