284 MANUAL OF TREE DISEASES 



duced which may be several inches long except in very young 

 trees where no swellings are noticeable. The trunk may 

 become infected by the fungus extending into it from infected 

 branches. The fruiting-bodies appear on the affected bark 

 in early spring. They are yellowish blisters, usually about 

 a quarter of an inch or smaller in diameter and may be longer 

 than broad. The covering of the blister breaks and the spores 

 are blown away as a fine' orange-colored powder. 



The spores from the yellow blisters infect the leaves and 

 younger stems of species of Comandra. Small yellowish or 

 reddish pustules are formed on light colored areas of the leaf 

 and a little later brown bristles project from the same spots. 

 The plants are dwarfed and often premature defoliation occurs 

 when the leaves are badly affected. 



Cavse. 



The Comandra rust of pines is caused by the fungus Cronar- 

 tium comandrcB {=Peridermium pyriforme Peck). The secio- 

 spores formed in the blisters on the pine bark cause the infection 

 of the leaves and young stems of Comandra. On that host 

 lu-ediniospores are formed which infect other Comandra plants. 

 The lU-ediniospores are closely followed by the production of 

 the bristle-like teliospore columns, the individual cells of which 

 germinate and produce the basidiospores. These latter spores 

 are wind-borne and may cause the infection of the pines, if 

 they are near by. Both the pines and species of Comandra 

 must be present in the same locality for this fungus to exist 

 on the pines. 



Control. 



The elimination of the species of Comandra from the vicinity 

 of nurseries and young plantations is necessary if this disease 

 is to be controlled. In the forest the diseased trees may be 

 destroyed as a measure of protection for the young growth 



