July 14,1923 
Degeneration Diseases of Irish Potatoes 
61 
characterization given is typical of Green Mountains in northeastern 
Maine and does not include variations due to environmental factors, 
degree of maturity, and current-season inoculation. It may be pointed 
out here that Quanjer (39, p. 140 ) suggests the possibility of viruses 
adapting themselves to new varieties, and that this in turn suggests the 
question of change of a virus in the same variety leading to new symptom 
complexes somewhat related to the old, as are streak and rugose mosaic 
current-season symptoms, mild mosaic and leaf-rolling mosaic, curly 
dwarf (combination of leaf-rolling mosaic and spindling tuber) and 
unmottled curly dwarf. Also, a varietal modification of a virus if occur¬ 
ring might be permanent even when the virus is returned to the variety 
originally affected. It may also be suggested that different viruses or 
causal agents may account for the differences in symptoms. 
Table VIII .—Symptoms and transmission of degeneration diseases of potatoes in the 
Green Mountain variety 
Name of disease. 
Size. 
Stem texture. 
Color. 
Leaf texture. 
Leaf form. 
Mild mosaic. 
Slight dwarfing. 
Distinct mot¬ 
Tenderness...... 
Wrinkling, ruf¬ 
fling. 
Wrinkling, ruf¬ 
fling, rolling. 
Wrinkling, ru¬ 
Leaf-rolling mo¬ 
saic. 
Rugose mosaic.. 
.do. 
tling. 
Indistinct mot¬ 
.do. 
Distinct dwarf¬ 
Brittleness.. 
tling. 
Mottling and 
Slight stiffness.. 
Streak. 
ing. 
Severe dwarfing 
after tuber 
perpetuation. 
Distinct dwarf¬ 
.do. 
slight chlorosis. 
Tenderness after 
gosity. 
Wrinkling, curl¬ 
ing, and rugos¬ 
ity after tuber 
perpetuation. 
Rolling. 
Slight rugosity 
Leaf roll. 
Rigidity.... 
Chlorosis. 
tuber perpetu¬ 
ation. 
Stiff and leath¬ 
Spindling - tuber 
disease. 
Unmottled curly 
dwarf. 
ing. 
Spindling.. 
Dark green early 
in season. 
ery. 
Slight stiffness.. 
Severe dwarfing. 
Brittleness.. 
early in season. 
Wrinkling, ruf¬ 
fling, rolling, 
curling, rugos¬ 
ity. 
Name of disease. 
Necrosis. 
Tuber symptoms. 
Transmission demon¬ 
strated. 1 
Incubation period. 
Mild mosaic. 
Leaf-rolling mosaic. 
Rugose mosaic. 
Streak. 
Leaf roll. 
Spindling-tuber dis¬ 
ease. 
Unmottled curly 
dwarf. 
Varying; more 
streaking from 
current - season 
inoculations. 
Streaking, spot¬ 
ting, leaf drop¬ 
ping, premature 
death. 
Burning. 
Burning, stem 
streaking. 
Browning near 
eyes. 
Grafts, aphids, and 
leaf mutilation. 
Aphids. 
Aphids and leaf muti¬ 
lation. 
Leaf mutilation 
Streaking (net ne¬ 
crosis). 
Spindling. 
Spindling, cracked. 
Grafts and aphids; leaf 
mutilation unsuc¬ 
cessful. 
Grafts, aphids, and 
leaf mutilation. 
Aphids and leaf muti¬ 
lation. 
Usually over 25 
days. 
Nearly like mild 
mosaic. 
About 14 days. 
About 12 days. 
Usually over 25 
days. 
Do. 
Do. 
1 Including intervarietal transmission into Green Mountains, as described in this paper. 
COMBINATIONS OF DISEASES 
When a certain symptom complex contains the symptoms of two or 
more of the several distinct diseases described in the preceding pages, 
and is associated with them, diagnostic evidence is therefore present, 
indicating that the former is a combination of the latter. Analytical 
