Proceedings 47 
The Economic Aspect of Fungus Diseases. 
I have thought that some remarks on the subject of those 
kinds of Fungi which do damage to cultivated crops and fruits 
might be of interest. The subject is one of very considerable 
economic importance, since the loss to every country through 
injury inflicted on cultivated plants by fungus pests must be es- 
timated at many millions of pounds annually. 
If we proceed to investigate the subject, we find that among 
the species of fungi which are doing this damage there are many 
whose life-history is either unknown or but very imperfectly 
known. But in a number of cases we find that scientific know- 
ledge has now been obtained both as regards the manner in which 
a particular species causing a certain disease lives and increases 
and also as to how it can be dealt with; such knowledge requires 
to be imparted to the practical grower. 
Looking at the subject from the economic point of view, we 
can divide fungus diseases of cultivated plants into two distinct 
classes. 
The first class consists of those diseases caused by species of 
fungi which are nof native to this country, but which have been, 
or are being introduced. For some time after being introduced 
such diseases are not very widespread, but are confined to certain 
districts. If, however, no concerted measures are taken against 
them, they soon spread through the country. That is to say, there 
is a class of fungi which ought to be dealt with dy /aw as ‘un- 
desirable aliens’ and immediately destroyed. It is a matter of 
opinion whether any human ‘alien’ should be considered undesir- 
able, but there can be no question, I think, that ‘alien’ fungus 
pests should be exterminated on arriving at our shores. 
The second class consists of destructive species of fungi which 
are widely spread and abundant everywhere, occurring practically 
in every garden or farm or fruit plantation. Such pests can be 
dealt with in two ways: (1), by taking remedial measures which 
are founded on a knowledge of the life-history of the particular 
species causing the disease; (2), by spraying the plant, on which 
the fungus grows and feeds, with certain chemical sprays. Such 
sprays are either protective, preventing the fungus from attacking 
the plant; or destructive, killing the fungus directly without injur- 
ing the plant. 
