412 



DISEASES OF ECONOMIC PLANTS 



spore. From this point of invasion the rot spreads in 

 every direction. When the rot reaches the trunk, it spreads 

 upward and downward and into all branches to which it has 



access. Thus trees, 

 hollow with rot, may 

 trace their downfall 

 to infection of some 

 small branch months 

 or even years earlier. 

 Care should be 

 exercised in feUing 

 trees to avoid injur- 

 ing other trees, and 

 in case of pruning- 

 wounds to apply 

 some antiseptic to 

 the exposed wound 

 to prevent the effec- 

 tive germination of 

 spores upon its sur- 

 face. Suitable anti- 

 septics are tar or 

 paint. 



Old, diseased trees 

 should be cut to prevent spread of infection to other trees. 

 Excision of the infected tissue can be practiced in case of 

 especially valuable trees. 



The fungi which cause these decays are manifold. In 

 some cases one species of fungus grows upon many different 

 kinds of wood. Other fungi are more particular as to their 

 food supply and are found upon fewer hosts. They chiefly 



Fig. 176. — Wound of properly removed limb be- 

 ginning to heal over. Ind. Agr. E.xp. Sta. 



