124 DISEASES OF GLASSHOUSE PLANTS 
a check either by reason of a prolonged spell of cold 
damp weather or some fault in crop management are the 
most susceptible to the disease, but otherwise temperature 
or shade have apparently no determining effect upon the 
incidence or progress of the disease. Control measures, 
thus, must be related to the growing of plants physio- 
logically robust, and to the control of biting insects 
which transmit the disease from plant to plant. The 
bacteria are readily carried on the hands and tools of 
the workers. After cutting a diseased plant, tools 
should be sterilized by wiping ona rag dipped in a two 
per cent solution of lysol or other disinfectant. Bacterial 
wilt is most serious at low temperatures, and raising the 
temperature of the houses until the average of day and 
night approximates to 90° F. has been found to check 
the disease. 
Foot Rot of the Cucumber and Melon 
A common disease of melons and cucumbers is that 
which is commonly called ‘canker’ by the practical 
man. It appears at the soil level, and is typically a 
rotting of the outer tissues of the stem at this part. 
These outer tissues soften, turn brown, and a rot begins, 
which spreads down into the roots as well as upwards 
along the main stem. Mainly it is confined to a region not 
more than six inches above soil level. The rot extends 
deep into the stem tissues and the disease organisms 
enter the wood vessels, ultimately causing the death of 
the plant (Fig. 33a), Under suitable conditions melons 
and cucumbers are so susceptible to the disease that the 
whole crop may be imperilled. Usually the disease does 
not show until the plants are eight to ten weeks old and 
are fruiting, but occasionally quite young plants are 
affected. 
The causal organism has been isolated and found to 
be Bacillus carotovorus, which causes a soft rot of many 
plants. 
