111] Finger and Toe, and Wart Disease 43 
growing immune crops the fungus cannot feed and so 
eventually it is starved. It has been found that it 
flourishes in sour or acid soils and not in soils con- 
taining a sufficient supply of lime. It is practically 
unknown on ordinary soils containing a high percentage 
of lime. This provides us with the key for solving the 
question as to why certain artificial manures favour 
the disease. Experiments have shown that Finger and 
Toe may become very bad on certain soils when acid 
manures are used in large quantities. Such manures 
as superphosphate and sulphate of ammonia use up 
the free lime in the soil and tend to make it sour. 
On soils liable to the disease through lack of lime 
these manures should be given up in favour of 
basic slag or bone meal and sodium nitrate, unless 
large quantities of lime or chalk are also used. It has 
also been shown that liming the soil keeps the disease 
in check. As soon as a diseased crop is raised 2 tons 
per acre of freshly slaked lime should be well spread 
over the surface. It is essential that the lime should 
be finely divided. If chalk is used about 4 tons per 
acre should be put on but it is not so effective. 
A similar dressing should be given about 18 months or 
six months before the next cruciferous crop is put on the 
soil. The object of putting on the lime is to get rid 
of the conditions favouring the growth of the fungus 
causing the disease. The lime also kills the spores 
with which it comes into contact. White turnips 
succumb more readily to this disease than swedes. 
It is important that the soil used as seed beds for 
cabbage should contain sufficient lime. 
