28 DISEASES OF GLASSHOUSE PLANTS 
by the individual crop requirement and cannot be 
performed by mere rule-of-thumb methods. 
Pruning and Training 
These processes are necessary for the production of 
clean, good quality fruit, for, as a general rule, plants 
which are pruned produce fewer flowers and fruits, but 
these are of a better quality than plants which are not 
pruned. Methods of pruning and training are of con- 
siderable importance in disease control. Not only does 
skilful pruning determine flower and fruit production, 
but by opening up the foliage it allows free circulation of 
air and prevents stagnation, which is so favourable to 
disease. At the same time the resulting wounds are 
important. All cutting should be done with a sharp 
knife, and the wound must be quite clean. Where 
leaves and laterals are removed, they must be cut off 
close to the point of origin. Stumps must not be left 
to dry up and decay, for these provide suitable entrances 
for fungi of all kinds. Even those fungi which normally 
do not attack the living plant may do so after growth on 
these half-dead tissues. It is especially important to’ 
realize this in tomato cultivation, where careless pruning 
and defoliation, which leaves jagged wounds, is the 
primary cause of stem rot by Botrytis sp. 
Disposal of Dead and Diseased Tissue 
The problem of destroying the remains of healthy 
and diseased plants is one which every grower has to 
face, and the degree of freedom from disease exhibited 
by his crops depends very considerably upon the 
thoroughness of this process. In many places the dead 
plants are allowed to lie for many months in large heaps 
close to the houses. The plants decay and become 
centres of infection from which disease is spread broad- 
cast. There is only one satisfactory way of disposing 
