DISEASES DUE TO FUNGI 81 
Control—Cultural Methods. 
Cultural methods for the control of the wilt have been 
devised and have been tested with promising results. 
It is commonly held by pathologists that plants 
exhibiting hard growth are more resistant to disease than 
the more succulent types, but observations on wilt disease 
show in this case the reverse to be true, the harder 
growing varieties succumbing more readily than the 
more succulent ones. The only variety, Manx Marvel, 
which so far has proved highly resistant to Verticalliwm 
shows a distinctly free growth with thick stems and large 
leaves. 
It has also been specially noted that plants, starved 
in the early stages, or having suffered from a severe 
check, are highly susceptible. It has been mentioned 
previously that the average temperature of the air and 
soil are limiting factors in the incidence of the disease. 
The disease is first seen in spring, when the temperature 
is low, but with the coming of the higher summer tem- 
perature the wilted plants recover, and the percentage 
mortality of the plants infected in the spring depends 
upon the length of time the cold weather lasts. 
The incubation period for the disease varies from 
eight to twenty days under favourable conditions, and 
complete wilt and death occurs in from six to eight weeks 
after the first symptoms appear, if conditions are favour- 
able for the fungus. Should the temperature be suffi- 
ciently raised before the plant dies it will recover and 
produce a satisfactory crop during such time as the 
temperature remains high. Once the temperature drops 
in the autumn wilt reappears and the plant dies pre- 
maturely. Early summer temperatures, therefore, enable 
the plants to resist the fungus. It will at once be evident 
that good results may be obtained by artificially shorten- 
ing the period of low temperature, and in glasshouses 
this may be done by increasing the boiler heat and 
closing down the houses in the middle of the day. 
The following cultural methods for controlling the 
c 
