6 BULLETIN 89, U.. S. DEPARTMENT OF AGRICULTURE, | 
NUMBER AND SIZE OF POPLAR TREES KILLED BY ARMILLARIA MELLEA. 
In addition to the dead chestnuts and oaks, the writer counted 29 
poplar trees which had been killed by this root-rot out of a total 
of 45 examined. Many of these were small and much suppressed, 
although there were 12 that ranged from 6 to 9 inches in diameter. 
These larger poplars were not suppressed and under normal condi- 
tions ought not to have died. 
GENERAL DISCUSSION OF THE DISEASED CHESTNUTS AND OAKS. 
Why a larger percentage of small white oaks should be killed than 
of small chestnut trees is difficult to explain from the data at hand. 
However, it seems to be evident, judging from the location of the 
smaller white oaks which were killed, that the majority of the trees 
under 11 inches in diameter were much suppressed and for this reason 
would perhaps succumb more quickly to disease than trees growing 
under more favorable conditions. Nothing was found to indicate that 
the larger white oaks which had been killed were in poor health 
before they were attacked by this disease. It would seem that the 
disease, having gained a foothold in the soil, simply spread to the 
large white oaks and finally killed them. As far as could be deter- 
mined, the fungus Armillaria mellea was the primary cause of their 
death. No white oaks in this region were seen which had been 
struck by lightning; this was in marked contrast to the number of 
chestnut trees in the same territory which had been struck. 
The only explanation which can be offered for the small percentage 
of young chestnut trees which had been killed by the root-rot is that 
the present stand of chestnuts originated mainly from sprouts, and 
the young trees therefore had the large root system of the parent 
stump from which to draw nourishment. As a result, their growth 
would be very vigorous during the first 10 or 15 years of life. Under 
such conditions one would not expect a hemiparasite like Armillaria 
mellea to attack them as readily as it did the suppressed young oaks. 
This, however, does not explain why the disease has killed so many 
of the older and larger chestnut trees, unless the old stumps acted 
as a breeding ground for the mycelium until it obtained a foothold 
in the living trees. The chestnuts undoubtedly were growing under 
unfavorable conditions, a fact proved by the very small annual incre- 
ment. This would make them more subject to diseases of this type. 
The weather conditions in the past may have been such as to weaken 
the trees and thus make them more susceptible to this rot. For 
instance, in the year 1913 the chestnut trees had lost two sets of leaves 
from late frosts, and at the time this investigation was made (June 
19, 1913) the third set of leaves was not fully developed, and many 
of the trees were so badly injured that they apparently were not 
going to leaf out at all. 
