2 BULLETIN 1461, U. ft. DEPARTMENT" OF AGRICULTURE 
It was soon realized, therefore, that any effective control measures 
must be based on a knowledge of the agencies by which the disease 
was carried over winter. The consequent studies of the overwinter- 
ing of cucurbit mosaic (#, 5) showed that it was not carried in the 
soil, nor, so far as could be determined, by insects. Experiments on 
the transmission of mosaic in the seed of the cultivated cucurbits in- 
dicated that this occurs so rarely, if at all, that it can not be con- 
sidered as a source of infection in the field. As a result of this nega- 
tive evidence, a study was made of the possible overwintering of the 
disease on wild host plants. 
The earlier investigations of this question proved that the wild 
cucumber, Micrampelis {Echinocystis) lobata (Michx.) Greene, was 
susceptible to mosaic and that, unlike the cultivated cucurbits, the 
disease was carried in the seed of this host (1, S). (PL 1.) Field 
observations showed that wild cucumber plants affected with mosaic 
appeared early in the spring and that the Diabrotica beetles fed on 
this host before cultivated cucurbits were planted and later trans- 
mitted the disease from the wild cucumber to the cultivated cu- 
curbits. Surveys during 1919 showed that mosaic wild cucumbers 
occurred in considerable numbers in districts where mosaic was prev- 
alent. In view of this correlation of the disease on the wild host 
with the presence of mosaic in the field, it was decided to attempt 
to control mosaic through the eradication of the wild cucumbers in 
certain sections where the disease was prevalent in the field. These 
earlier experiments were located chiefly at Rockland, Wis., and 
Marengo, 111. 
In each case an area was selected which included a number of 
cucumber fields in which mosaic was reported to have caused severe 
injury in previous years. The removal of the wild cucumber plants 
in these areas was undertaken before cucumbers had been planted 
in the field, and after the first eradication the areas were again in- 
spected at intervals of 10 to 14 days for the greater part of the sea- 
son. The wild cucumber is usually found on low, moist ground, but 
has been used extensively as an ornamental and is often abundant 
in the vicinity of towns. In the eradication work it was found 
that the plants were commonest along small streams, in hedgerows, 
and about farm buildings. Only a small percentage of the plants 
were found to be affected with mosaic, but these mosaic plants fre- 
quently occurred in the vicinity of cucumber fields. All the wild 
cucumbers were removed throughout the experimental area regard- 
less of the presence of mosaic. Practically all the plants in the area 
were found during the first inspection, but where large groups of 
plants occurred along wooded streams or ditches an occasional plant 
was found during later inspections. In all this work the wild cu- 
cumbers were merely pulled out and allowed to remain where they 
were found. 
EXPERIMENTS OF 1920 
ROCKLAND, WIS. 
Experimental work at Kockland, Wis., in 1920 included an area 
of approximately one-half square mile. Ten fields in this area were 
planted to cucumbers, most of the fields being within a radius of 
one-fourth of a mile of the village of Rockland, which was included 
