56 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
ticable method of controlling the disease has appeared to consist 
of the early removal of the wild host plants which represent the 
original sources of infection. Field experiments have been in pro¬ 
gress for the past three years in an effort to determine the practical 
possibilities of controlling the disease by the eradication of these 
wild hosts and the work is being continued. As a result of this 
work the host range of cucurbit mosaic has been found to be larger 
than was at first suspected and the eradication program has con¬ 
sequently been somewhat enlarged. The evidence obtained up to 
the present indicates definitely that wild host plants are probably 
responsible for practically all the primary infection on the cultivated 
cucurbits. The practical possibilities of controlling the disease 
by the eradication of these host plants have not as yet been fully 
worked out, but recent results have offered considerable encourage¬ 
ment. 
SUMMARY 
Continued investigations of the overwintering of cucurbit mosaic 
have shown that the disease does not persist in the soil. 
Further trials with the seed of mosaic cucumber, squash, musk- 
melon, and pumpkin plants indicate that seed transmission of the 
disease probably does not occur or is so rare as to be of little signifi¬ 
cance. 
There is no evidence that the striped beetle ( Didbrotica vittata ) is 
an agency in overwintering cucurbit mosaic. 
Cucurbit mosaic is transmissible through the seed of the wild 
cucumber (Micramvelis lobata) and the disease is transmitted from 
this host to the cultivated cucurbits by the cucumber aphis (Aphis 
gossypii), the striped beetle, (Diabrotica vittata) , and the 12-spotted 
beetle (Z). 12-punctata) . The striped beetle is the chief agency in 
transmitting the primary infection from the wild cucumber to the 
cultivated cucurbits, as this insect first feeds on the wild host and 
later migrates to the cultivated cucumbers. Field experiments 
indicate that the beetles may thus carry infection over distances of 
at least 400 yards. 
Surveys of cucumber-growing districts in Wisconsin and northern 
Illinois indicate that the wild cucumber is an important factor in 
overwintering mosaic. 
The milkweed (Asclepias syriaca) is susceptible to cucurbit mosaic, 
and is important as a means of overwintering the disease. Mosaic 
lives over in the roots of the milkweed, and mosaic plants are often 
found in the vicinity of cucumber fields. The cucumber aphis feeds 
on the milkweed and acts as a carrier of the disease from this host 
to the cucumber. Observations indicate that most mosaic milk¬ 
weeds are originally infected from adjacent cucumbers. In many 
localities the milkweed appears to be of more importance than the 
wild cucumber as a source of infection to the cultivated cucurbits, 
as the mosaic plants usually occur in the immediate vicinity of the 
fields. 
The pokeweed (Phytolacca decandra) is susceptible to cucurbit 
mosaic, and the disease found on pokeweeds in the field is trans¬ 
missible to the cucumber. Mosaic lives over winter in the roots of 
the pokeweed, and the cucumber aphis acts as a carrier of the disease 
from the pokeweed to the cucurbits. Mosaic pokeweeds are rare in 
