July 1, 1925 
Overwintering and Dissemination of Cucurbit Mosaic 
39 
Table XV. — Results of cross inoculations from mosaic pokeweeds to healthy 
cucumber and muskmelon plants by means of aphids 
Date of 
inoculation, 
Method of inoculation 
1922 
Number 
of aphids 
per plant 
Number 
of plants 
inocu¬ 
lated 
Number 
of plants 
mosaic 
Date 
ob¬ 
served, 
1922 
Cucumber 
Feb. 15. 
Feb. 24. 
Do- 
Mar. 15. 
Do 
Mar. 16 
Mar. 20 
Do. 
July 10. 
Do. 
Aug. 21. 
Do. 
Aug. 22. 
Do. 
Aug. 24 
Do- 
Aphids from mosaic pokeweed plant. 
-do... 
Aphids from healthy pokeweed plant (control).. 
Aphids from mosaic pokeweed plant_ 
Aphids from healthy pokeweed plant (control).. 
Aphids from mosaic pokeweed plant.. 
_do.... 
Aphids from healthy pokeweed plant (control).. 
Aphids from mosaic pokeweed plant. 
Aphids from healthy pokeweed plant (control).. 
Aphids from mosaic pokeweed plant. 
Aphids from healthy pokeweed plant (control) 
Aphids from mosaic pokeweed plant... 
Aphids from healthy pokeweed plant (control) 
Aphids from mosaic pokeweed plant. 
Aphids from healthy pokeweed plant (control).. 
25 
10 
10 
15 
15 
15 
15 
15 
15 
15 
15 
15 
15 
15 
1 
4 
2 
2 
2 
2 
10 
4 
8 
4 
49 
28 
12 
12 
15 
12 
1 
0 
0 
0 
0 
1 
9 
0 
4 
0 
25 
0 
11 
0 
11 
0 
Feb. 20 
Mar. 13 
Do. 
Mar. 22 
Do. 
Mar. 20 
Mar. 24 
Do. 
July 16 
Do 
Aug. 31 
Do. 
Do. 
Do. 
Do. 
Do. 
Muskmelon 
Aug. 4.. 
Do. 
Aug. 25. 
Do- 
Aphids from mosaic pokeweed plant. 
Aphids from healthy pokeweed plant (control)— 
Aphids from mosaic pokeweed plant__ 
Aphids from healthy pokeweed plant (control).. 
30 
30 
15 
15 
3 
3 
12 
12 
3 
0 
9 
0 
Aug. 14 
Do. 
Sept. 1 
Do. 
* Aphids allowed to transfer naturally from mosaic and healthy pokeweed plants in the respective cages. 
jroduce mosaic shoots during the following year. Roots from such 
dants were collected at Anna in 1923 and taken to Madison, Wis. 
.n all cases they produced mosaic shoots, and infection was produced 
>y inoculation from these plants to the cucumber. Pokeweeds 
inoculated from mosaic cucumber plants were planted in the open at 
Madison in the summer of 1922 and the plants were allowed to over¬ 
winter. Most of these plants were winterkilled, but the few which 
survived produced mosaic shoots during the spring of 1923. It has 
also been found that when the top of a mosaic plant is cut back to the 
roots the new shoots are always mosaic diseased. It appears, there¬ 
fore, that the mosaic disease which affects the pokeweed in the field 
is transmissible to the cucurbits and that the disease is carried over 
winter in the roots of the mosaic plants. 
Trials with Seed from Mosaic Pokeweeds 
In addition to the trials with roots of mosaic plants, seed from 
mosaic pokeweeds has also been tested in order to determine whether 
the disease is carried over winter in this manner. A considerable 
amount of seed was collected for the writers by E. A. Bierbaum at 
Anna, Ill., during the summer of 1922, from both mosaic and healthy 
pokeweeds. As in the case of the trials with seed from the milkweed, 
the seed was planted in flats of sterilized soil in the greenhouse and 
grown at a temperature of approximately 28° C. Seed from healthy 
pokeweed plants was used as a control. These trials included about 
800 seedlings from mosaic plants, but there was no evidence that the 
disease is carried in the seed. This evidence of nontransmission of 
pokeweed mosaic in the seed is in keeping with observations made by 
W. W. Gilbert at Donaldson, Ind., in 1922, and by the senior author 
at Anna, Ill., in 1923. At both points it was found that cucumber 
