LEAF DISEASES AND INJURIES 39 



not assumed such general importance and are only found de- 

 structive to certain species in restricted areas. In California, 

 white and Shasta red fir, lodge-pole, western yellow, and Jeffrey 

 pine are frequently affected by leaf-cast. In the Northwest, 

 leaf-cast occurs destructively on western yellow and white pine 

 and on western larch. In eastern United States, white pine 

 and balsam fir are sometimes affected. 



Symptoms. 



The general symptoms of leaf-rast are similar in a way to 

 sun-scorch and other injuries which cause the needles to die 

 and tm-n reddish or brown. In leaf-cast, however, the first in- 

 dication of the disease is the appearance of yellowish or brownish 

 bands or spots on the needles. The needles do not suddenly 

 tin-n brown at the tips or in their entirety as is the case when a 

 lack of water causes the death of the needles. Also in leaf- 

 cast, the needles of a single bundle or twig are usually not all 

 affected simultaneously. After a needle shows the brown 

 spots, it soon turns yellow or brown and may fall off. Some- 

 times the twigs are affected and they are either stimulated to 

 form witches'-brooms or are killed. 



The fruiting-bodies of the causal fungi appear as roundish or 

 elongate black pustules on the surface of the affected leaves. 

 The fruiting-bodies may not be formed until the leaves fall to 

 the ground. When closely examined, a narrow line will be 

 seen running lengthwise of the fruiting-body and dividing it 

 into halves. In the spring the two halves break apart at this 

 line and fold backward, exposing the spores. 



Caiise. 



The leaf-cast diseases of conifers are caused by several species 

 of fungi belonging to the closely related genera, Lophodermium, 

 Hypoderma and Hypodermella. In this country the following 

 species have been found to cause leaf-cast : — 



