362 
Journal of Agricultural Research 
Vol. XXX, No. 4 
SUMMARY 
A mushroom root rot of grapevines, 
of rather common occurrence in various 
localities in the Ozark section of Mis¬ 
souri, is reported and described in de¬ 
tail. The organism isolated from the 
roots of the diseased vines proved to 
be a very slow-growing but distinctive 
one, developing characteristic sub¬ 
merged rhizomorphs in the cultures. 
Fruiting bodies, w^hile not associated 
with the diseased vines first studied 
in the field, were subsequently de¬ 
veloped in some of the cultures. But 
a few days before the first fruiting 
bodies were secured in the cultures a 
species of Clitocybe was observed 
fruiting abundantly at the bases of 
rotted grapevines in a vineyard in 
another section of the State and in an 
oak forest a few miles distant. Cul¬ 
tures of the fungus isolated from the 
roots of these vines yielded a rhizo- 
morph-producing organism identical 
with the one isolated from the first 
material studied. Although no oppor¬ 
tunity of reproducing this root-rot 
disease by inoculations with pure cul¬ 
tures of the fungus isolated from in¬ 
fected vines has been afforded, it is 
believed that beyond all doubt the 
disease in question is caused by this 
rhizomorph-producing organism. 
The fungus which is believed to be 
the causal organism is a species of 
Clitocybe described by various writers 
in this country under the names C. 
monadelpha , C . aquatica , Armillaria 
mellea exannulata, and C. parasitica , 
all of which are clearly different 
names for the same plant and identical 
with Clitocybe iabescens of Europe. 
A detailed discussion is given of the 
history, nomenclature, and geographic 
distribution of this fungus, together 
with complete lists of the synonyms 
and illustrations believed to be au¬ 
thentic. 
A detailed description is given of the 
characteristics and behavior of the 
Clitocybe root-rot fungus in pure cul¬ 
tures and a comparison is made be¬ 
tween the form isolated from grape¬ 
vine roots in Missouri and one secured 
from a eucalyptus root from Florida. 
Although the writer's cultures of the 
Missouri form of Clitocybe root rot 
were generally much slower in their 
development and in the production 
of fruiting bodies than the Florida 
form, the two agreed so closely in 
their morphological characters that he 
is of the opinion that these two forms 
represent but two rather widely dif¬ 
fering strains of the same fungus. 
Although Clitocybe tabescens in the 
United States is known to occur from 
New York south to Florida and west 
to Michigan, Kansas, and Texas, 
cases of root rot caused by this fungus, 
with the exception of those in a few 
middle eastern States, have been 
reported only from the southern part 
of the country, where it appears to be 
of most widespread occurrence. The 
losses occasioned to vineyards in 
Missouri by Clitocybe root rot, which 
appears to be a comparatively slow- 
working disease, vary from the death 
of a few vines each year in cases of 
mild attack to such rapid destruction 
that within a few years parts of the 
vineyard may be heavily depleted. 
Clitocybe root rot is a disease 
associated with lands which formerly 
were covered by hardwood timber, 
especially oak. The disease appears 
to be practically unknown in strictly 
prairie soils and in old land, except at 
the margins in close proximity to 
timbered lands. It has been found to 
attack grapevines and fruit trees 
chiefly in places where the soil is 
poorly drained, either as the result of 
natural depressions in contour or in 
places underlaid with a more or less 
impervious soil or hardpan. 
Attention directed in the selection 
of vineyard sites to the thorough prep¬ 
aration of newly cleared timberlands, 
adequate drainage of any spots in need 
of it, and prevention of barking or 
other injury of the vine roots when 
cultivating the vineyard, will prove 
valuable measures in preventing at¬ 
tack by Clitocybe root rot. In case 
the disease is observed in vineyards 
already established, adequate drain¬ 
age, which is and will always remain 
the most valuable remedial measure, 
should be assured, and the spread of 
the disease may then be checked by 
the prompt removal of all badly 
diseased and dead vines, the chemical 
treatment of adjacent vines, and the 
disinfection of the soil before replant¬ 
ing. The various methods for the 
destruction of the fungus on newly 
infected vines and in the soil are 
briefly reviewed and the need for 
further experimentation is pointed out. 
Comparatively little study has been 
made of the fungi causing root rot of 
grapevines in this country. Although 
cases of this disease have been reported 
in various sections since its discovery 
in Missouri in 1887, it has, with few 
exceptions, been attributed to Armil¬ 
laria mellea and Dematophora necatrix, 
as a rule on assumption, however, 
rather than from definite knowledge. 
