6 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
In addition to this 80 cucumber plants were set out on May 20 
in the vicinity of cucumber fields where mosaic had occurred during 
the previous season. Several groups of Micrampelis plants, 110 in 
all, were also planted about the edge of a field where the disease 
seemed to occur earliest each season. All of these plants were 
attacked by the beetles to some extent, but none of them became 
infected with mosaic until late in the season. 
Further trials were made during the spring of 1921 with 452 beetles 
collected in the neighborhood of cucumber fields between May 25 
and June 4. The insects were fed on healthy cucumber plants in 
the same manner as in previous trials, a total of 176 plants being 
used in the experiments. All these plants remained healthy. 
The results of these and earlier experiments (8) indicate that the 
beetle does not carry the disease through the winter, and the evidence 
is strengthened by experimental data which indicate that after 
feeding on mosaic plants they carry the virus for only a short period. 
The trials with beetles from hibernation cages were, however, the 
only ones of definite value in this regard, since it has been found 
that the wild cucumber, on which the insects feed after emerging 
from hibernation, is often affected with cucurbit mosaic. Infection 
obtained from beetles taken in the open, therefore, is not conclusive 
evidence that they carry the disease overwinter. 
OVERWINTERING OF THE MOSAIC DISEASE ON WILD HOST PLANTS 
Since the seed of the cultivated cucurbits seems practically elimi¬ 
nated as a carrier of cucurbit mosaic, and since neither the soil nor 
insects appear to be concerned in overwintering the disease, atten¬ 
tion has been focused on the possible existence of wild host plants 
which carry the disease from year to year and serve as sources of 
primary infection to the cultivated cucurbits. As a result of these 
studies; it has been found that the wild cucumber, Micrampelis 
lobata , the milkweed, Asclepias syriaca L. ( 9 ), the poke weed, Phyto¬ 
lacca* decandra L. {10), and probably certain Physdlis spp., are im¬ 
portant factors in overwintering the disease. 
RELATION OF THE WILD CUCUMBER TO THE OVERWINTERING OF CUCURBIT MOSAIC 
Efforts to connect the wild cucumber, Micrampelis lobata, with the 
overwintering of mosaic arose from the fact that this plant is common 
throughout the cucumber-growing sections of the Middle West and is 
affected with a mosaic disease identical in appearance with that 
occurring on the cultivated cucurbits. Furthermore, the wild 
cucumber is frequently used as an ornamental vine on fences and 
porches and is often found in the vicinity of cucumber fields (pi. 1, A). 
Observations made during 1917 and 1918 {8) showed that wild 
cucumbers growing at certain points became mosaic-diseased year 
after year and that the disease appeared on these plants consider¬ 
ably earlier than in adjacent cucumber fields. As the wild cucumber 
is an annual, it was thought that the disease in these cases must be 
carried in the seed, although there was little evidence of seed trans¬ 
mission in the case of the cultivated cucumber. An extensive trial 
of seed from mosaic Micrampelis plants was made in 1918, but, 
owing to unfavorable greenhouse conditions, the results were nega¬ 
tive (8). A further trial during 1919 (7), however, gave apparent 
evidence of seed transmission which has been confirmed by the 
results of the additional tests during the last three years. 
