256 PLANT DISEASES 



attacked, the consequence being that the leaves fall quite 

 early in the season, and the new growth is small in 

 quantity and imperfectly matured. In the case of full- 

 grown pear trees, the loss of the leaves early in the 

 season prevents the formation of a good supply of reserve 

 material, and consequently a poor crop of fruit the follow- 

 ing season. 



Preventive Measures. — Spraying with fungicides is 

 of no practical use. The one important point to clearly 

 understand is the fact that the fungus produces two different 

 kinds of fruit on different host-plants. The plum tree, 

 hawthorn, or whitebeam can only be infected by spores 

 from the stage growing on juniper ; whereas the juniper 

 can only be infected by aecidiospores formed on one of 

 the host-plants enumerated. Abolish one of the host- 

 plants and the mischief ends. Infection has been known 

 to take place when the two host-plants were half a mile 

 apart, the spores being carried by the wind. When it is 

 desirable to retain both trees concerned, then spare no 

 trouble in discovering the juniper producing the teleuto- 

 spores, the gelatinous orange masses being quite con- 

 spicuous in the spring. The most certain method is to 

 completely remove the infected branches, if this can be 

 done without disfiguring the tree, as the mycelium of the 

 fungus is perennial and extends far into the wood, and is 

 with difficulty destroyed. If it is not desirable to cut out 

 the diseased juniper branches, remove the bark from the 

 diseased portion, wash with a strong solution of sulphate 

 of copper or corrosive sublimate, and afterwards cover the 

 wound with grafting wax, or paint over with tar. Even 

 after this treatment a strict watch should be kept on the 

 branches each spring, otherwise the mycelium present in 



