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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
Considerable increase was noted on two-year trees, and while variable, 
about 18 per cent of the two-year stock was usually affected with 
isolated cankers on the trunk or limbs. In three-year stock and older, 
over 50 per cent was found to be cankered while in some blocks of 
two or three hundred trees, none were found free from the disease, and 
the greater part were wholly or partially dead from the severe attacks 
of numerous trunk cankers. 
The species of Populus found to be attacked by Dothichiza are the 
following: P. nigra var. italica, Lombardy poplar; P. alba var. pyra- 
midalis, Bolle’s poplar; P. balsamifera, balsam poplar; P. trichocarpa, 
black cottonwood; P. deltoides, cottonwood; P. eugenei, Carolina 
poplar; P. angulata, hybrid Carolina poplar. Of these all but the first 
two mentioned are meeting with less favor as shade or ornamental 
trees and are being gradually discarded by nursery men. Another 
species not mentioned in the list, like Japan poplar (P. maximowiczii) 
was found in two nurseries and should meet with more popularity 
on account of its attractive foliage, its shapely head, its hardiness, 
and the fact that none had been attacked by Dothichiza. Some 
inoculations were made by Mr. F. M. Trimble of the Pennsylvania 
Bureau of Economic Zoology, to test the immunity of this tree. The 
results of these inoculations will be of interest this coming spring. 
If any conclusions can be drawn regarding the relative susceptibility 
of the various species of poplar attacked, they would receive the most 
support from a comparison of the number of diseased trees of each 
species, and the relative virulence of the attacks. That the Lombardy 
poplar is the most susceptible seems borne out by the fact that this 
species has the greatest percentage of infected trees. The degree of 
virulence is fully as great, however, in all of the other species subject to 
the canker, with the exception, perhaps, of the Carolina poplar. The 
latter species was able to produce such a vigorous growth of cambium 
that in most cases the wounds produced by the canker were entirely 
healed over. On the other hand, where heavy pruning offered many 
wounds on the trunk for the entrance of the spores from which cankers 
developed, the trees were unable to overcome the injuries. 
Nurserymen have noted cankers on Lombardy poplars for several 
years, and estimates ranged from three to thirty years. No serious 
affection among poplars was reported, however, until 1915, when “a 
badly diseased condition of black poplars was reported to the U. S. 
Department of Agriculture. In the spring of 1916 numerous com¬ 
plaints were received of a serious blight on freshly transplanted black 
poplars.” 1 The presence of Dothichiza populea was found to be 
1 Hedgcock, Geo. C. and Hunt, N. Rex. Dothichiza populea in the United States. 
Mycologia, vol. VIII: 300-308. 
