APPLE DISEASES 109 
for at least a half century. It is now found on practically every 
continent of the globe. Records come from Europe, South 
Africa, Asia, New Zealand and 
North America. It occurs in 
practically every state in the 
Union, but is most abundant in 
the more southern states of the 
apple-growing belt, from Virginia 
to Texas. The disease is also 
known in Canada. 
As already intimated, crown- 
gall is most damaging in the 
nursery, and becomes most 
prominent and important where 
root-grafts are carelessly made. 
In many instances the affected 
plant shows no ill effects, and 
trees are said to outgrow the 
disease if they are well rooted. 
In certain other cases affected 
plants are dwarfed, which of 
course renders them less valu- 
able. A common source of loss 
lies in the fact that other patho- 
genes enter plants through the 
gall-lesions. 
Symptoms. 
The disease may exhibit itself 
in two forms: (1) as galls (Fig. 
30), and (2) as hairy-roots (Fig. 
31). The galls are either hard or 
soft and occur at the ground- 
Fic. 30.— Crown-gall on apple 
roots. 
line or on limbs. It is estimated that fully 90 per cent of 
the galls appear, in the nursery, on the scion just above the 
