266 REPORT OF THE No. 3 



(4) A Poplar Canker. 



Early in May, 1921, an examination was made for the Toronto Harbor 

 Commission of a plantation of about 500 Lombardy poplars planted out in 

 the fall of 1920 on the Lake Shore road, York County, which were found to be 

 affected with a canker disease caused by an imported fungus, Dothichiza populea, 

 Sacc. & Briard. Fully 80 per cent, of the trees were diseased, and all were cut 

 down and destroyed. This fungus, apparently, found its way into America 

 originally from Europe in nursery stock, and in the present instance there is 

 every probability that the disease was already established in the young trees 

 when they left the local nursery from which they were obtained. A visit to 

 the nursery in question at the time, resulted in finding the disease in the re- 

 maining stock of Lombardy poplars. The causal fungus attacks the trunks 

 and branches of trees of all ages, killing them outright or permanently disfigur- 

 ing them; but it is especially virulent in newly transplanted trees and in stock 

 heeled in for early spring planting. Besides the Lombardy poplar, it is also 

 known to attack the cotton wood, populus deltoides. To what extent other 

 poplars are susceptible is not known, but it seems worth while that this feature 

 should be watched. It is also certain that there should be the closest inspec- 

 tion on the part of nurserymen and of those who purchase poplars from nurs- 

 eries. 



This disease was reported for the first time in America by Hedgcock & Hunt 

 in 1916 (Hedgcock, George C. & N. R. Hunt: Dothichiza populea in the United 

 States, Mycologia 8, pp. 300-308, 2 plates, 1916), but was known thirty years 

 or more prior to that in Europe, especially in France, Germany and Italy. 

 Specimens were received by the writer from an eastern source in Canada in 191" 

 through the courtesy of the Dominion Botanist. In Europe, populus deltoides 

 seems quite as liable to attack as populus nigra, and in France severe losses 

 have been experienced in plantations of the former grown for timber. 



The causal lungus attacks the bark, killing the cambium. In such spots, 

 the bark becomes more or less sunken, but not much discolored (Figure 4). 

 These depressed areas or cankers rapidly extend in all directions, and as a result, 

 girdling commonly takes place. Pustules soon appear on the cankers, and from 

 them emerge countless numbers of tiny spores which serve to transmit the 

 parasite to other hosts. Diseased trees in nurseries or in plantations should 

 be cut down and burned. 



I have the honour to be, sir, 



your obedient servant, 



E. J. ZAVITZ, 



Provincial Forester. 



Toronto, Ont., October 31st, A.D. 1921. 



