192 MANUAL OF TREE DISEASES 



fruiting-stage, as described under symptoms, is known. Spores 

 are produced in abundance from the fruiting-bodies (pycnidia) 

 during wet weather and may be washed or spattered by rain to 

 neighboring trees. The first infections take place in the lateral 

 twigs, which are quickly killed. The mycelium then spreads 

 into the main stem and proceeds upward, killing the outer wood- 

 tissues and cambium on one side of the tree and running out 

 into other laterals. 



Control. 



Experiments so far tried in spraying with lime-sulfur and bor- 

 deaux mixture for the control of this disease have not been suc- 

 cessful. The period of infection extending throughout the grow- 

 ing-season and the nature of the scale-like leaves and the twigs 

 preclude much hope of good results from spraying. Careful 

 eradication of all diseased and neighboring trees may, to some 

 extent, reduce losses by stopping the enlargement of the spots 

 in the beds. 



Reference 



Hahn, G. G., Hartley, Carl, and Pierce, R. G. A nursery blight of 

 cedars. Jour. Agr. Res. 10 : 533--539, pis. 60-61. 1917. 



Leaf- and Stkm-Rusts (General) 

 Caused by species of Gymnosporangium 



Several species of the rust-fungi belonging to the genus Gym- 

 nosporangium cause more or less important diseases of juniper 

 and cedar. These fungi are strictly parasitic and never grow 

 except in the living tissue of some plant. They are, therefore, 

 confined to the range of the species of juniper and cedar, which 

 are foimd in the north temperate zone in North America, 

 Europe, Asia and northern Africa. Another important pe- 

 culiarity of these fungi which further restricts the range of each 

 species is that they each require certain kinds of broad-leaf trees 



