40 MANUAL OF TREE DISEASES 



On white and pitch pine and hemlock in eastern United States, — 

 Hypoderma strobicola Tubeuf = Lophodermium brachysporum Rostnip. 



On balsam flr in eastern United States, and white and Shasta red 

 fir in California, — Lophodermium nervisequum, Fries. 



On western larch in the Northwest — Hypodermella laricis Tubeuf. 



On western yellow pine in the Northwest, — Hypoderma deformans 

 Weir. 



On lodge-pole pine in California, — Hypoderma sp. 



On western yellow pine in California, — Lophodermium sp. 



To the unaided eye, the fruiting-bodies of these fungi are all 

 similar. The roundish or elongate black raised pustules mature 

 during the winter. With the coming of warm spring rains, the 

 fruiting-body splits along the median cleavage line and the two 

 valve-like halves are folded back. In this condition the layer 

 of asci containing ascospores is exposed. The spores are shot 

 into the air and are disseminated by the wind. If all the spores 

 are not ejected the first time, subsequent rain periods will cause 

 further spore-ejection. In this way the periods of infection 

 may be distributed in dry climates over the entire growing 

 season. Where rain periods are more frequent in the spring, 

 most of the infection occurs in May and June and the supply 

 of spores is exhausted. The needles of the ciu-rent season 

 only are affected in the case of some of the leaf-cast diseases, 

 while in others the older needles are affected and the young 

 needles remain healthy. The mycelium in some cases enters 

 the twigs and may induce the formation of witches'-brooms, or 

 the affected twig may be killed outright. 



Control of leaf -cast diseases. 



In the forest no measures of control are practicable. In 

 nurseries the trees may be sprayed with bordeaux mixture. 

 The mixture should be applied before the rain periods which 

 cause the ejection of the spores. In order to avoid the expense 

 of spraying for these diseases, nurseries should be located at a 

 distance from coniferous forests and thus avoid chances of 

 infection. ^ 



