species, strains, and even hybrids, according to the studies of 
Dr. Ir. H. van Vloten*. Some of the American Melampsoras are 
different from those in Europe. Some poplar species and hybrids 
are much more susceptible to certain rusts than other poplars; in 
fact, some poplars are so susceptible that their growth is greatly 
reduced and they are valueless for planting. 
57. European bacterial canker was noted in some nurseries and 
plantings from which cuttings had been distributed. Populus species 
and hybrids vary in susceptibility to this disease, some being 
highly susceptible. This disease is not known in America. 
58. In Italy, there is a new canker disease of poplars, and ac- 
cording to discussions with Dr. G. Scaramuzzi**, there is still 
considerable doubt about the cause. It threatens to become serious 
on some poplars. 
59. In southern Denmark I examined a forest planting of poplars, 
perhaps 30 to 40 feet tall, that was being seriously damaged by 
some disease with which I was not familiar. According to two of 
the foresters, this disease had only been noted in the last 2 or 3 
years in areas where the poplar clone had been growing’ for many 
years previously without trouble. My kodachromes showing trees 
of one poplar clone attacked by this disease, with nearly all of the 
leaves and small twigs dead and brown in contrast with trees of 
adjoining clones with all leaves a healthy green, are quite striking. 
60. In Holland, Dr. van Vloten and I found the Septotinia leaf 
blotch in a poplar planting, the first report for Holland. The deter- 
mination of the fungus was made by Alma Waterman and Edith K. 
Cash ***, who recently published on this leaf blotch of many kinds 
of poplars. This leaf disease was first reported from Latvia in 
1932 and it is thought the few infections in the United States are 
from an introduction from Europe. The conspicuous white fruiting 
bodies on the leaves make the disease one that is easily detected 
= _ Dr.Ir.H.van Vioten. Crossing experiments with strains of Melampsora 
Leet rn a Overdruk uit het “Tijdschrift over Plantenziekten,” 
** Baldacci, E., R. Ciferri, M. Orsenigo, and G, Scaramuzzi. Osserva- 
zioni sul “cancro batterico” del pioppo in Lombardia. Notiziario sulle 
malattie delle piante. Istituto di Patologia Vegetale dell’Universita Milano, 
via Celoria 2, N.9, Marzo- Aprile 1950. Pp. 15-25. 
*** Waterman, Alma M., and Edith K. Cash. Leaf blotch of poplar caused 
by a new species of Septotinia. Mycologia XLII (3) : 374-384. 
May - June, 1950. 
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