80 
years in the given district, and by choosing early varieties 
it is possible to avoid this disease to some extent. 
It is even more important, however, to endeavour to 
prevent the first outbreak of the disease in a given area. 
All possible sources of infection such as diseased tubers 
and stalks should be carefully collected and burned at 
the end of the season. Since the disease is propagated 
from year to year in slightly diseased tubers, seed potatoes 
should only be used from a crop which never showed 
any sign of the disease even on the leaves. 
We have seen that tubers become infected either, by 
the growth of fungus down the stalks, or by spores being 
washed into the soil. If, therefore, the attack occurs late 
in the season all haulms should be removed and destroyed 
before the tubers are lifted; and infection from the latter 
source may be prevented, to some extent, by seeing that 
the tubers near the surface are well covered with soil. 
This should be done as soon as possible after the haulm 
has died down, for apart from the-risks of the Phytoph- 
thora disease, tubers left too. long in the ground are 
more liable to be attacked later by rots in the store. 
The tubers should be stored under dry conditions in such 
a way that air has free access to them, and diseased 
haulms should never be used for covering the “pie” or 
clamp. ; ; 
; if potato plants are sprayed three or four times at 
fortnightly intervals, beginning when they are about six 
inches high, it. should usually be possible to prevent any 
serious epidemic in a given field or garden. Much can 
also be done to prevent infection by the immediate destruc- 
tion of diseased tubers and haulms, and by only using 
seed potatoes from a perfectly healthy crop. By such 
recautionary measures, in addition to the use of varieties, 
ee by experience to be resistant in the district, it 
should be possible to reduce the effects of this disease to 
a minimum. 
