32 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE. 
become profitable, or when the trees have attained the age of 8 or 10 years, they begin 
to rot off at the crown and die. This is especially true of apples. I have particularly 
in mind a thriving orchard in the Southeast of 25 acres of apple trees, 11 years old, 
which bore a few crops, then all at once about half of them began to fall. Upon 
examination it was found that the trees had been killed by crown-gall. 
Van Deman (70), in a discussion on fungous diseases, is quoted as 
follows, in a Virginia Horticultural Society Report, in answer to a 
question concerning an apple tree diseased with crown-gall: ‘‘ Yes, sir; 
it lives right along until it begins to bear, and then it begins to dwindle, 
and you wonder why. * * * It doesn’t attain the size of other 
trees, though sometimes it is fairly vigorous. The gall will, however, 
keep on growing for years and years.” 
Popenoe (44) reports the following Snes: A lot of Ben Davis 
trees, 2 years old, one half having visible galls on the roots and the 
other half being similar trees without galls, were planted a few years 
ago on rich, second-bottom, level, black land on the station grounds 
at Manhattan. At the time the report was made, in 1903, Popenoe 
says: ‘‘There is practically no difference in the growth above ground 
of the trees of the two lots, and of the trees originally clean of galls, 
ome are now affected.’ 
OBSERVATIONS BY OTHERS ON HAIRY-ROOT. 
In the various citations as to the effect of crown-gall on trees there 
is little or no reference to hairy-root. Stewart, Rolfs, and Hall (64), 
referring to the hairy-root of seedlings, which we have designated as 
the simple type, state that ‘‘affected trees are worthless for planting.” 
Garman (16), discussing a knot disease of apple trees which is evi- 
dently the aerial form of hairy-root of the woolly-knot type, makes 
the following statement: 
It undoubtedly weakens the trees attacked, but does not keep them from bearing 
in all cases, and when but few knots are present the trees show no other outward 
evidence of disease. 
In a letter dated September, 1907, Garman writes as follows con- 
cerning the disease: ‘I am satisfied it is not spreading, and I do not 
regard it as particularly destructive, although I have no doubt it 
affects the health of the tree when a great many of the knotty growths 
are present.” 
The gist of the foregoing quotations, which include a summary of 
nearly everything that has been published on the effects of crown- 
gall and hairy-root in this country, is that in the opinion of a majority 
of those observers who have investigated these forms of disease, they 
are to be considered dangerous and likely to weaken or kill affected 
trees. This general opinion concerning the nature and effect of 
crown-gall of apple trees seems to have gained ground largely as a 
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