MISTLETOE INJURY TO CONIFERS. rate 
GENERAL SUPPRESSION AND FUNGOUS ATTACK. 
Aside from the fact that fungous enemies enter these conifers 
through broken branches, lesions, and burls caused by mistletoe, 
heavily infected trees are, owing to their weakened condition, more 
susceptible to fungous attack on any part—roots, trunks, or leaves. 
In the lake region of Idaho the larch of all ages and conditions is 
at present suffering from an epidemic of a needle disease, Zypoder- 
mella laricis Tub. It is observed that in practically every instance 
the needles of very old mistletoe brooms are first attacked, whereas 
those of the uninfected trees of particular age classes or exposures 
may ward it off for a longer period.t. It is a common observation 
that in regions of heavy mistletoe infection (and nowhere is it better 
shown than in the forests of eastern and central Oregon and many 
parts of Idaho and Montana) many heavily infected trees are in 
a dead and dying condition. If these trees are carefully examined 
with reference to average healthy growth for the region, it will be 
found that they have died prematurely. 
It has already been indicated that mistletoe is capable of causing 
the death of its host in some instances. The whole tendency of the 
parasite is to reduce the life functions of its host to the lowest point, 
and if death does not result from this cause alone the way is opened 
to various secondary agents, which may or may not attack vigorously 
growing trees. The gradual thinning out of the foliage of heavily 
infected trees and the appropriation by the brooms of much of the 
elaborated food materials must necessarily result in an unbalanced 
relation between the crown and the root system. Consequently, there 
‘may be a dearth of food materials for the latter, wholly inadequate 
to support its present extent. It may be naturally inferred that this 
results in the suppression of the roots or a dying off of the more 
extended members of the system. A close examination of a hundred 
or more windfalls of heavily infected Douglas fir, yellow pine, and 
larch in the regions above mentioned shows quite clearly that the 
horizontal and brace roots of these trees in most cases were badly 
decayed. Since few windfalls of the heavily uninfected trees of 
the same average age and size were observed in the same region, 
it may be inferred that a possible relation existed between the sup- 
pressing effects of the mistletoe and the decay in the roots. <Armil- 
laria mellea (Vahl.) Quél. was definitely associated with some of 
the decay in the roots. In most cases, however, owing to the absence 
of fruiting stages, the cause of the rot in the fallen trees could not 
be determined. 
1 Hypodermella laricis was first named and described by Von Tubeuf on the European 
larch (Lariz europaea). This is the first note of its occurrence in North America. The 
fungus, characterized by its four clavate spores to an ascus, is very destructive and is the 
cause of considerable damage in the larch forests of the northwestern United States and 
Canada. 
