44 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE, 
COMMUNICABILITY OF THE DISEASE IN THE NURSERY AND THE 
ORCHARD. 
PREVIOUS PUBLICATIONS ON THE COMMUNICABILITY OF APPLE 
CROW N-GALL. 
Ever since crown-gall and hairy-root have been brought to the 
attention of plant pathologists one of the chief problems under dis- 
cussion was related to the question of whether these forms of disease 
are communicable, especially under nursery and orchard conditions. 
As a matter of precaution, growers have been generally advised to 
refrain from planting diseased trees, and their destruction, both in 
the nursery and the orchard, has been recommended. In some cases 
trees to the extent of a carload at a time have been condemned by 
zealous nursery inspectors and destroyed on account of the presence 
of diseased trees.? 
The earlier accounts of the fae by W. E. Smith (56), Yates (80), 
Bailey (5), and others, are based upon the idea that the disease is 
probably not communicable, but later researches have overthrown 
this theory. 
Woodworth (78) recommends rejecting all affected stock, purchas- 
ing from nurseries known to be entierely free from crown-gall, burn- 
ing diseased trees, and devoting fields in which the galls have appeared 
to some other crop for a number of years. 
Toumey (68), in his work on the crown-gall of the almond, records 
an experiment in which he attempted to transfer the disease from 
the almond to the apple, both by soil inoculation and by graft inser- 
tion, but was unable to communicate the disease. ? 
Selby (52) recommends the destruction of all affected stock, and 
Says: 
Soil which causes this sort of growth upon peach trees in the nursery has been known 
to produce the same upon the apple, and conversely. 
Garman (15) makes the following statement, without citing proofs: 
It has been demonstrated that crown-gall is a contagious disease, to be conveyed to 
seedling trees by crushing the galls and putting them in soil in which seeds are planted. 
Trees grown with others that are galled are therefore not above suspicion, even when 
they show no outward evidence of the disease. 
Guilford (17), speaking of apple crown-gall, says: 
For the past three years I have been trying to inoculate the Virginia crab roots with 
this gall. Conditions were made favorable by wounding the roots and covering them 
a Paddock, Wendell. Crown-gall. Bulletin 86, Colorado Agricultural Experiment 
Station, 1903, p. 5. 
6 Dr. Erwin F. Smith has shown the writer large, hard crown-galls on apple stems 
produced by him in 1908 by pure-culture inoculations of Bacterium tumefaciens 
obtained from the soft crown-gall of the peach. 
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