6 CEOWN-GALL AND HAIRY-KOOT DISEASES OF THE APPLE TREE. 



budded trees (PI. I, figs. 3 and 4) by a stunted root system, accom- 

 panied with an excessive production of small fibrous roots, often origi- 

 nating- in clusters from the main root, or taproot, (lalls often occur 

 in connection Avith hairy-root, but these are a result of wounds rather 

 than a form of this disease. Seedlings of the hairy-root t3'pe, unless 

 wounded, remain free from galls. 



TYPES OF APPLE CROWN-GALL. 



Apple crown-gall is of two types. A hard callous form is common 

 on grafted trees at the union of the root and scion, and at any other 

 point of the root system where wounds occur in either the cultivation 

 or transplanting of trees (PI. I, fig. 1). The results of extensive inoc- 

 ulations with this type have failed to prove that this disease is of a 

 contagious nature. 



A second type is a soft form more common on seedlings (PI. 11, 

 fig. 2), occurring more rarely on grafted trees (PI. I, fig. 2). These 

 softer galls resemble those of the raspl)erry and peach, in that they 

 are soft and often rot off. It is not certain, however, that they, like 

 the latter, are replaced the following year by a new gall growth from 

 the adjacent live tissues of the host, nor is there proof yet that they 

 are of a contagious nature. 



EFFECT UPON THE LENGTH OF LIFE OF THE APPLE TREE. 



Careful data are being collected from orchards and nurseries as to 

 the effect of these diseases upon the life and fruitfulness of trees. 

 Any information as to the locality of orciiards in which diseased trees 

 have bee-n planted w^ill be highly appreciated. In our crown-gall 

 orchard there are more than 200 trees diseased with the hard type of 

 crown-gall, and 20O healthy trees of the same grade planted under 

 similar conditions. After two years' growth six of the crown-gall 

 trees and nine of the healthy ones have died. No difference in the 

 growth of the trees is noticeable. However, it can not be assumed 

 from the results so far that, on the one hand, the disease may not yet 

 shorten the life of the trees, or, on the other, that the trees may not 

 entirely overcome its effects. A tree having crown-gall on its roots, 

 however, can never be correctly graded with a smooth-rooted tree. 

 The root system of a healthy fibrous-rooted apple tree is shown in 

 Plate III, figure 1. 



SUGGESTIONS TO NURSERYMEN. 



Nurserymen are advised to be careful in the selection of seedlings 

 for grafting and budding. All rough, warty, or galled seedlings 

 should be thrown out, for most of them will form rough-rooted trees. 

 Seedlings with tufted or hairy roots should also be rejected, for these, 



