July 14,1923 
Degeneration Diseases of Irish Potatoes 
87 
found this species to be a transmitting agent. It will be noted (Series 9) 
that aphids from potato inoculated with tobacco mosaic were non- 
infectious, indicating that potato was not a susceptible masking host or 
symptomless carrier. Aphid colonies did not establish themselves on 
the tobacco plants inoculated with potato mosaic, for a corresponding 
test of tobacco as a symptomless carrier of potato mosaic. A number of 
control inoculations from healthy plants of one species to the same in the 
other were made, but are of no significance in view of the negative results 
from mosaic inoculations. 
Table XXI .—Mosaic inoculations between potato and tobacco ( Orono , Me., winter of 
IQIQ-20) 
Series. 
Source of inoculum. 
Method of inoculation. 
Inoculated plants. 
I 
Mosaic potato. 
Juice stabbed in Feb. 
Five, tobacco, largest leaf 10 
2 
.. .do. 
28; leaf mutilation 
Mar. 9,15, and 24. 
Leaf mutilation Mar. 6- 
cm. long Feb. 28. Healthy 
Apr. 26. 
Two, potato, 2 cm. tall Mar. 
3 
...do. 
9, 15, and 24. 
Spinach aphids, 25 to 
6-9. Healthy Apr. 26. Sec¬ 
ond generation, 8 of 9 tuber 
units mosaic. 
Ten, tobacco, with 3 to 6 leaves 
4 
...do. 
100 to a plant, Feb. 5 
or 17. Fumigated 5 
to 7 days later. 
Spinach aphids, 60 to 
over 1 cm. long when inocu¬ 
lated. Healthy Mar. 26. 
Two, potato, 8 cm. tall when 
5 
Mosaic tobacco.... 
200 to a plant, Jan. 16 
or Feb. 3. 
Leaf mutilation Mar. 
inoculated. Mosaic in 29 to 
32 days. Second generation 
mosaic. 
Four, potato, 2 cm. tall Mar. 
6 
...do. 
5-9, 16, and 24. 
Leaf mutilation Feb. 16. 
5-9. Healthy Apr. 26. Sec¬ 
ond generation healthy. 
Five, tobacco, with 6 or 7 leaves 
7 
...do. 
Spinach aphids, 10 to 80 
over 1 cm. long when inocu¬ 
lated. Mosaic Mar. 2 and 
possibly before (PI. 15, B). 
Eight, potato half-tubers, with 
8 
Mosaic potato. 
to a half-tuber, Apr. 
14. Fumigated Apr. 
21. 
Spinach aphids, 25 to 
sprouts 2 to 5 mm. long. 
Plants healthy. 
Seven, potato half-tubers, with 
9 
Inoculated pota¬ 
100 to a half-tuber, 
Apr. 14. Fumigated 
Apr. 21. 
Spinach aphids Apr. 3... 
sprouts 2 to 5 mm. long; 
4 of the 7 plants mosaic by 
June 26, and 5 by July 21. 
Tobacco, with leaves not over 
10 
to, of Series 5. 
None. 
None. 
2 cm. long. Healthy Apr. 26. 
Control parts of tuber units of 
Series 2,4, 5,7, and 8healthy. 
Second generation of Series 2, 
4, and 5 also healthy. 
Control tobacco, healthy Apr. 
2. (See Series 6.) 
Tobacco, healthy (PI. 15, B). 
11 
12 
_do. 
As for Series 1. 
Leaf mutilation once.... 
*3 
14 
*5 
As for Series 2. 
As for Series 5. 
Mosaic potato. 
....do . 
Growth in soil recently 
Potato. Healthy in first genera¬ 
tion. Mosaic in 8 per cent of 
the second. 
Potato, healthy. 
Many seedlings in 5 pots, 
occupied by diseased 
plant. 
healthy 6 weeks after germi¬ 
nation. 
