July i, 1925 Overwintering and Dissemination of Cucurbit Mosaic 
31 
At Rockland the fact that mosaic milkweeds were found near 
cucumber fields only was emphasized by surveys during 1921 and 
1922. Over an area of 2 square miles, which included 10 cucumber 
fields, an effort was made to locate as many milkweed plants as 
possible and some hundreds of plants were examined during both 
seasons. Only two groups of mosaic plants were found at a dis¬ 
tance of more than a few yards from cucumber fields. On the other 
hand, seven groups of mosaic milkweeds were found growing either 
in and immediately adjacent to fields of cucumbers or on land 
which had grown cucumbers in 1920. Two of these groups were at 
the same points where mosaic plants were found m 1920. The 
mosaic milkweeds at the different points varied in number from 3 to 
100, and most of them were found between June 10 and July 20. In 
three instances the mosaic milkweeds were between rows of cucum¬ 
bers. In four of the other six groups they were on land where 
mosaic cucumbers had grown in 1920. In all cases the mosaic plants 
were within 50 yards of cucumber fields, and as aphids were present 
during the latter part of July there was ample opportunity for the 
transmission of the disease to the cucumbers. It was not possible 
to trace the first mosaic infection on the cucumber to the milkweed 
as directly as in 1920, but in one field the first mosaic cucumber 
E lants were found growing about a mosaic milkweed plant which 
ad appeared late in the season. 
At Marengo only five groups of mosaic milkweed plants were 
found during the season of 1921. The area covered was much 
larger than at Rockland, and the cucumber fields were scattered 
and at considerable distances from one another. Four of the five 
groups of mosaic milkweed plants were found on land which had 
S rown cucumbers in 1920. Mosaic milkweeds were found in this 
eld in 1920 and infection also occurred on the cucumbers during 
that year. In two of the four cucumber fields in which mosaic 
milkweeds were found in 1921, infection appeared three weeks earlier 
than in any of the remaining nine fields in the area examined. In 
every case where mosaic milkweeds were found the land had grown 
several successive crops of cucurbits. 
At both Rockland and Marengo mosaic milkweed plants were 
found before cultivated cucurbits had appeared, so that this source 
of infection was present from the beginning of the season. Most of 
the mosaic milkweeds appeared during June and early July, but in 
some cases mosaic plants were found just breaking ground during 
the latter part of August. Aside from obtaining the data just re¬ 
ferred to, little survey work has been done with regard to milkweed 
mosaic. Mosaic milkweeds were found in 1920 in three cucumber 
fields on Long Island, N. Y., in which nearly all of the cucumber 
plants were affected with mosaic. A further inspection of fields of 
other crops showed a large number of milkweeds in the vicinity, 
but no mosaic milkweeds were found at such points. Mosaic milk¬ 
weed plants were also noted during 1921 at Sparta and Portage, 
Wis., and at Harvard, Ill. 
It is evident from these observations that mosaic milkweeds, while 
comparatively rare, occur in most cases in the immediate vicinity of 
cucumber fields, or on land which has previously grown cucurbits. 
In view of the fact that practically no mosaic is found on milkweed 
plants in isolated situations or on farms where cucurbits are not 
