176 TREES AS GOOD CITIZENS 



shaped top, and the stems are swollen at the base. These 

 two characters often are unreliable as the ring is frequently 

 evanescent and the swollen base usually is not very pro- 

 nounced. Trees which are badly afflicted with this form 

 of rot should be cut down, and it is not safe to replant in 

 the infected soil. 



Coral red spots about the size of a pin's head on the 

 bark of trees and shrubs are symptoms of a disease com- 

 monly called Nectria Cinnabarina canker, a fungous 

 growth closely related to the rusts of leaves, which finds 

 entrance through small surface wounds. It produces bluish 

 or blackish streaks in the wood. Once established, it has 

 a tendency to spread to other trees or plants. This disease 

 may be cured by cutting and burning all affected bark 

 and wood and washing the wound with solution of copper 

 sulphate, using i pound to 5 gallons of water. The exposed 

 surface should then be coated with coal tar. As with 

 other diseases, prevention is better than remedy, and if all 

 wounds are promptly treated when created, the spores will 

 find no means of entry. 



Black knots sometimes appear on twigs and leaves of 

 Cherries, Plums and allied trees but rarely on shade trees. 

 While they are not serious, they are unsightly. They may 

 be controlled by cutting and burning in the early fall and 

 spraying with either copper sulphate or lime sulphur before 

 the buds open in the spring. 



"Witches' Broom" is a conspicuous growth which is 

 frequently seen and which impairs a tree's appearance. It 

 consists of masses of short twigs, so bunched as to cause 

 them, in some instances, to be mistaken for mistletoe. This 

 disease is caused by a fungus or an insect, often a mite. 

 It may be controlled by cutting and burning the affected 

 parts. Although mistletoe is a parasite plant it is not a 

 fungus, but belongs to the group of flowering plants to 



