12 BULLETIN 1461, U. S. DEPARTMENT OP AGRICULTTOE 
plants of these species are more likely to occur near garden plots 
as a result of earlier infection from cultivated cucurbits. 
If possible the field should be surrounded by other cultivated 
crops, since their cultivation vv-ill reduce the number of wild hosts 
about the field. It has also been found that fields so situated are less 
likely to be infested with insect carriers of the disease. 
All plants which are known to carry mosaic over winter should 
be removed from the field itself and from all land within a radius 
of 50 to 75 yards. This includes the wild cucumber, milkweed, wild 
ground cherry (Physalis), pokeweed, and catnip. All of these 
hosts may not occur in one locality, but some of them appear to be 
common in most cucumber-growing sections in the Central and 
Eastern States. In the case of the wild cucumber, milkweed, ground 
cherry, and catnip, the plants should be dug out if they are not too 
abundant, but it has been found that if the shoots are pulled up 
as fast as they appear the plants eventually will die out. Where 
pokeweeds occur it is best to cut down as far as possible into the 
large roots and cover the cut surface with salt. If the field receives 
the clean cultivation that cucumbers require, many of the wild hosts 
will be removed in the process. The first eradication should be 
made just before planting, and the field and vicinity should be 
inspected regularly thereafter at intervals of 3 to 10 days. Frequent 
inspections are essential owing to the fact that perennial hosts 
such as the milkweed and ground cherry will often fail to send 
up shoots for some time and then suddenly develop them in large 
numbers. Experience has shown that such eradication work in the 
case of the average field requires only 5 to 10 hours of additional 
labor during the season. 
All cucumber plants in which mosaic appears early in the season 
should be removed in order to prevent the further spread of the 
disease. 
Since the disease is carried from the wild hosts to the cucumber 
by means of insects, the field should be sprayed- or dusted regularly 
in order to keep down plant lice and cucumber beetles. 
The writers believe that if the above-described procedure is care- 
fully followed the losses from mosaic in the average field can be re- 
duced to a point where they are not of serious importance. It must 
be realized, however, that where fields lie close together it is almost 
essential that all the growers cooperate in removing the sources of 
infection about their fields. 
SUMMARY 
Field experiments on the control of cucumber mosaic by the eradi- 
cation of the wild host plants on which it overwinters were conducted 
in Wisconsin and Illinois from 1920 to 1924. When these experi- 
ments were undertaken it was known that mosaic was carried in the 
seed of the wild cucumber, Micrampelis {E chinocystis) lobata, and 
as the work progressed it was also found that the disease overwin- 
tered in the roots of the following perennials : Milkweed (Asclepias 
b-ijriaca) , pokeweed {Phytolacca decandra) , ground cherry {Pkysalis 
heterophylla and P. subglabrata), and catnip (Nepeta cataria). Cer- 
tain of these hosts occur in all the cucumber-growing sections of the 
Eastern and Central States. 
