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EXPERIMENTS:«witH NursERY STooK. 645 
doubt that the infected twigs are the principal means by which 
the fungus is carried through the winter and the presence of an 
aScigerous form, described by Sorauer, seems almost unnecessary 
to a maintenance of the disease in a region once infested. 
The practice of allowing stocks to remain in the nursery rows 
when the leaf-blight has affected them so severely as to render 
them unbudable seems unwise when considered from a hygienic 
standpoint. Such stocks are almost sure to harbor the parasite 
in its winter form upon their slender branches, which are lacking 
in vigor. It is from these stocks that the disease apparently 
spreads to other plantings of seedlings in the vicinity, and to such 
budded stocks as are susceptible. It would seem advisable, there- 
fore, that when leaf-blight causes a large number of failures in the 
seed bed the diseased seedlings should be headed back to within 
one or two inches of the ground and all side shoots likely to harbor 
the parasite removed. Such procedure would undoubtedly 
decrease the liability to so early an attack of the disease and 
enable growth to be made before the malady had time to spread 
from infected localities. The same immunity as that shown by 
rapidly growing “buds” may prove here a valuable factor. It has 
been objected, however, that the simultaneous appearance of 
several shoots from the headed-back seedling would prevent, or at 
least hinder severely, the budders in their work the following fall. 
This obstacle could be overcome by the early removal of all but one 
shoot. It seems to me that this method of eradicating the disease 
is sufficiently promising to warrant a thorough test. The matter 
of protecting seedlings by wind-breaks has not been thoroughly 
tested to my knowledge, and from observation on the spread of this 
disease I am inclined to believe it is worthy a systematic trial. 
Thei freedom from leaf-blight, which isolated blocks of pear seed- 
lings often show, tends to confirm the observation that the malady | 
travels quite slowly from seedling to seedling. In an experimental 
block of seedlings mentioned below it required nearly two months 
for the disease to travel from the east to the west end, a distance 
of 150 feet. 
