TREE DISEASES AND TREATMENT 177 



which its possible hosts, the trees and shrubs, also belong. 

 Its part in romance and sentiment does not begin until 

 the twigs reach the drawing room. On its host the mistle- 

 toe is a parasite, sapping its strength and retarding its 

 growth. The damage starts when the mistletoe dies, 

 for in the process of decay it leaves a cavity which 

 affords a means of entrance for other more harmful dis- 

 eases. If allowed to flourish, mistletoe becomes a serious 

 enemy. It may be controlled by cutting it away com- 

 pletely and treating the cavity as recommended in previous 

 chapters. 



Various fungous diseases attack the foliage of trees 

 and these may be the cause of much damage, since it is 

 through the agency of green leaves that a plant gets its real 

 nourishment, and any reduction in the foliage decreases 

 the tree's food supply. In addition to this definite damage 

 the loss of leaves mars the tree's appearance. If the 

 growth persists for a single season only, the damage is not 

 important; but if it proceeds unchecked for several years, 

 the tree becomes badly weakened and may die. 



Protection against these diseases is largely by means 

 of spraying. The effectual materials are spoken of as 

 fungicides, the most useful of which are Bordeaux mixture 

 and ammoniacal copper carbonate. The former is the 

 least injurious to foliage, while likely to discolor buildings. 

 The latter is safer near buildings, but needs to be very 

 carefully made and applied in order not to injure the 

 foliage. 



Bordeaux Mixture. Bordeaux mixture is composed 

 of copper sulphate (bluestone) and quicklime, with a 

 certain quantity of water. The amounts of copper sul- 

 phate and of lime to be used with a given quantity of 



water vary somewhat, according to the kind of trees to be 

 12 



