July i, 1925 Overwintering and Dissemination of Cucurbit Mosaic 
15 
Table VI. — Transmission of cucurbit mosaic to healthy cucumber plants by striped 
beetles collected from groups of mosaic Micrampelis plants 
Date 
Num¬ 
ber of 
bee¬ 
tles 
in 
cage 
Num¬ 
ber of 
plants 
in 
cage 
Num¬ 
ber of 
plants 
mosaic 
Date observed 
Date 
Num¬ 
ber of 
bee¬ 
tles 
in 
cage 
Num¬ 
ber of 
plants 
in 
cage 
Num¬ 
ber of 
plants 
mosaic 
Date 
observed 
June 15,1919... 
74 
16 
3 
July 1,1919 
May 28, 1920. _ 
39 
12 
0 
June 14,1920 
Do. 
57 
20 
6 
Do. 
June 7,1920_ 
41 
12 
0 
June 18,1920 
June 18,1919... 
40 
10 
2 
Do. 
Do.. 
52 
15 
2 
Do. 
Do_ 
61 
12 
0 
Do. 
June 14,1920... 
35 
10 
0 
June 29,1920 
June 20, 1919... 
25 
9 
1 
July 5,1919 
Do_ 
35 
10 
0 
Do. 
June 29,1919... 
40 
12 
0 
July 12; 1919 
Do.... 
35 
10 
3 
Do. 
May 28, 1920... 
50 
14 
2 
June 14,1920 
The infection which occurred in 7 out of the 13 cages represents a 
fairly high percentage of infection in the case of the striped beetle, 
since many trials with beetles taken directly from mosaic cucumber 
plants have shown that relatively few such insects will transmit the 
disease. A considerable number of insects were placed in each cage, 
as the percentage of infection with the individual insects had always 
been low. This is in marked contrast to the results with the cucum¬ 
ber aphis, Aphis gossypii; but, as stated in an earlier paper (£), it is 
probably due partly to the fact that the beetle, a chewing insect, 
often attacks the stems and blossoms of the plant and, in a majority of 
cases, probably does not produce infection in wounds at these points. 
The results of artificial inoculation have shown that relatively little 
infection takes place through superficial injuries in the blossoms or 
on the surface of the stem. 
DISTANCES OYER WHICH MOSAIC MAY BE TRANSMITTED FROM MOSAIC MICRAMPELIS 
PLANTS BY CUCUMBER BEETLES OR OTHER INSECTS 
Although mosaic Micrampelis plants are a possible source of pri¬ 
mary infection to cucurbits m the field, their importance in this con¬ 
nection rests to a great extent on the distances over which insects 
may transmit the disease from such plants. As already noted, the 
striped beetle, and to a lesser extent the 12-spotted beetle, seem the 
most important agents in such transmission, for they probably 
migrate more commonly and to greater distances than do aphids. 
An effort has been made to determine experimentally the distance 
which the disease may be transmitted by insects, in the belief that 
such transmission would most probably be through the agency of 
the cucumber beetle. Such experiments were necessarily only 
indicative, but were undertaken in the hope of accumulating some 
actual data on the spread of mosaic about a single group of mosaic 
wild cucumber plants. 
An effort was made to remove all known or suspected host plants 
of cucurbit mosaic over a certain area, with the exception of a single 
"group of mosaic Micrampelis plants which was left as a source of 
infection. wSmall plats of cucumbers were planted at varying dis¬ 
tances from these wild cucumber plants, and under such conditions 
any mosaic occurring on the cucumbers could be traced with some 
certainty to the group of mosaic wild cucumbers. The area used 
for these experiments was nearly all under cultivation and almost 
free from known hosts of cucurbit mosaic. It extended north from 
