14 
1ST. C. Experiment Station 
tributed by the implements used in cultivation, by the use of soil in inocu¬ 
lating with the nodule forming organism, by rains, or by being harvested 
with the hay crop. If this hay is fed to stock the possibility exists of 
the return of these sclerotia to the fields through the manure. 
The violent discharge of ascospores from the mature apothecia and 
the carriage of these spores by the air currents may also be taken into 
account in the local spread for short distances of the stem rot fungus. 
Methods of Control 
A very considerable body of data and observations bearing on methods 
of control have been presented in published accounts of stem rot. Much 
of the experimental work is of value, however, only inasmuch as it indi¬ 
cates methods which cannot be employed with success. In the light of 
the facts which have been presented relative to the life history of the 
causal fungus, some of these experimental results are to be anticipated. 
This may be instanced by the work with fertilizers and manures at the 
Rothamsted Experiment Station (16) which was based on the assump¬ 
tion that “clover sickness” is due to unfavorable soil conditions. TsTo 
appreciable differences in treated and untreated plots were noted, results 
in agreement with those of Rehm (18) and others who have performed 
less extensive tests. Among the different fertilizers which have been 
applied are guano, barnyard manure, compost, bone meal, woodaslies, 
gypsum, and lime. In the Essex experiments (1), where ground lime¬ 
stone was employed, clover remained free from disease. Causes other 
than the use of lime are believed to have been operative in this case, since 
these results do not accord with those just presented nor with the more 
recent ones of Coleman (4). 
Among the cultural practices which have been noted to be of benefit 
by Ereckmann (8) and Gilbert and Myer (10) are deep plowing. This 
was suggested from experiments by Rehm (18) in which sclerotia were 
buried at different depths in garden loam. Ho apothecia were developed 
when sclerotia were covered as deep as eight cm., about 3 inches. Rehm 
further pointed out that buried sclerotia were subject to destruction by 
earthworms, wireworms, millipeds, and mites. During the season of 
1917 the sclerotia which were covered with sand in the studies on apoth- 
ecial development were, in several series, noted to be completely de¬ 
voured by fungus gnats, Mycetophilidae. The burial of sclerotia par¬ 
ticularly when the soil is kept moist favors their decay from natural 
causes. Complete decay of the sclerotia of Sclerotinia trifoliorum was 
observed by the writers to be accomplished within two months. Stevens 
and Hall (24) have reported that under natural conditions the number 
of sclerotia of S. libertiana is greatly reduced by decay. 
