July 1,1925 Overwintering and Dissemination of Cucurbit Mosaic 
53 
the disease from the cucumber rather than the pigweed on which 
they were collected, further experiments were undertaken in which 
mosaic pigweeds were first freed from aphids by spraying and then 
covered with insect-proof cages. After sufficient time had elapsed 
to insure the plants being free from insects, aphids were transferred 
to the pigweed from healthy cucumber plants. At the same time, 
other aphids from the same healthy cucumber plants were placed 
on healthy pigweeds under separate cages. Ten days later the 
aphids on both the healthy and mosaic pigweeds were transferred 
to separate lots of healthy cucumber plants under cages in the 
greenhouse. The cucumbers on which tne aphids from the mosaic 
pigweeds were placed developed mosaic in a majority of cases, 
while the control plants remained healthy. Inoculations were also 
made by artificial methods from mosaic pigweeds to cucumber 
plants, both in the field and greenhouse. In these inoculations 
the crushed leaf tissues of the mosaic plant, inserted in longitudinal 
incisions made in the stem of the cucumber, were used as inoculum. 
As shown in Table XXIII, a high percentage* of infection resulted 
from this method as well as from the use of aphids. 
Table XXIII. — Cross inoculations from mosaic plants of Amaranthus retroflexus 
to healthy cucumbers 
Date of inoc¬ 
ulation 
Aug. 12,1920. 
Do. 
Aug. 13,1920_ 
Do_ 
Aug. 18,1920-.. 
Do_ 
Do. 
Do_ 
Do. 
Do. 
Do_ 
Do_ 
Sept. 2,1920-. 
Do_ 
Sept. 4,1920. _ 
Do_ 
Do.— 
Do_ 
July 15,1922... 
Do_ 
June 30,1923. 
Do_ 
Method of inoculation 
Location 
Number 
of plants 
inocu¬ 
lated 
Number 
of plants 
mosaic 
Date ob¬ 
served 
Aphids from mosaic pigweed plant_ 
Greenhouse. 
6 
6 
Aug. 22,1920. 
Aphids from healthy pigweed plant 
_do_ 
6 
0 
Do. 
(control). 
Artificial .. 
Field_ 
8 
6 
Aug. 25,1920 
Do. 
Control.i_ 
.do_ 
8 
0 
Aphids from mosaic pigweed plant_ 
_do—_ 
8 
7 
Sept. 1,1920 
Aphids from healthy pigweed plant 
_do_ 
6 
0 
Do. 
(control). 
Aphids from mosaic pigweed plant_ 
Greenhouse _ 
7 
7 
Do. 
Aphids from healthy pigweed plant 
.do.. 
7 
0 
Do. 
(control)." 
Artificial_ 
_do_ 
8 
2 
Do. 
Control . _ _ 
_do_ 
6 
0 
Do. 
Artificial__ ___ 
Field_ 
12 
3 
Do. 
Control. . _ __ 
_do_ 
8 
0 
Do. 
Artificial 
—do.— _ _ 
10 
6 
Sept. 13,1920 
Do. 
Control.. ___ __ 
_do_ 
6 
0 
Artificial _ __ _ 
_ ..do. 
6 
5 
Do. 
Control... __ _ 
. ..do_ 
6 
0 
Do. 
Artificial__ 
Greenhouse _ 
4 
1 
Do. 
Control___ 
_do_ 
4 
0 
Do. 
Aphids from mosaic pigweed plant_ 
_do_ 
12 
12 
July 25,1922 
Aphids from healthy pigweed plant 
_do_ 
10 
0 
Do. 
(control). 
July 7,1923 
Do. 
Artificial . __ _ _ 
.do_ 
6 
3 
Control ___ 
_do—_ 
6 
0 
CROSS INOCULATION FROM MOSAIC CUCUMBER PLANTS TO THE PIGWEED 
As a result of the successful inoculations fromjnosaic Amaranthus 
plants to the cucumber, efforts were made to transmit cucurbit 
mosaic to this host. Aphids from mosaic cucumber plants were 
transferred to the leaves of healthy pigweeds growing under cages in 
the greenhouse, and aphids from Tiealthy cucumber plants were 
E laced on other pigweeds as controls. The inoculated plants had 
een grown from seed in the greenhouse and were from 6 to 12 inches 
tall. At the end of 7 days the inoculated plants showed a slight 
