314 
Journal of Agricultural Research 
Vol. XXVIII, No. 4 
Table X.— Age of sugar beet plants in relation to susceptibility 
Season, experiment, 
and date 
Insects 
per plant 
Number of plants 
Age of plants 
Inocu¬ 
lated 
Diseased 
Season of 1920: 
No. 1, January 2... 
No. 2, March 13_ 
6 to 8 leaf stage..._ _. 
1 
35 
22 
1 
6 
2 
{o to^7 leaf stage...... 
1 
6 
0 
No. 3, March 17_ 
/Cotyledons and first pair of leaves .... 
1 
6 
4 
17 to 8 leaf stage_2_____ 
1 
6 
1 
No. 4, March 31_ 
/Cotyledons and first pair of leaves ... 
1 
15 
8 
1 6 to 8 leaf stage___ 
1 
15 
1 
No. 5, April 2_ 
/Cotyledons and first pair of leaves___ 
1 
15 
15 
12 
3 
\6 to*8 leaf stage....... 
1 
No. 6, July 14. 
5-months old!....... 
2 
20 
0 
Season of 1921- 
No. 7, July 2_... 
J4 months old _ _____ 
2 
10 
1 
\2 mrmt.hs nlri 
2 
11 
2 
No. 8, September 20. 
No. 9, October 14. _ 
8 to 9 leaf stage....... 
2 
6 
1 
10 to 16 leaf stage... . 
2 
14 
1 
OTHER PLANTS SUSCEPTIBLE TO CURLY-TOP 
A list of plants found susceptible to curly-top has been previously given ( 8 ). 
Since that time no extensive effort has been made to determine what other 
plants may be affected by the disease. The annual (redmaids) Calandrinia men- 
ziesii T. and G., may now, however, be added to the list of those plants proved to 
be susceptible (PI. 5, A and B.) This species is of special interest in this connec¬ 
tion because it is one of the early winter annuals and probably serves along with 
(alfileria) Erodium cicutarium in harboring the curly-top virus over winter. 
Among cultivated plants the tomato, Lycopersicon esculentum Mill, may now 
be included among the susceptible species. The effects of the disease on th e 
tomato are rather of the mosaic type, a clearing of the veins of the younger 
leaves which gives these a slightly mottled appearance and a curling and distor¬ 
tion of the youngest leaves. Affected plants gradually wilt, turn yellow, and die 
within a few weeks after infection. The disease has not been found in commer¬ 
cial plantings, so far as is known to the writers. This is probably explained by 
the fact that the tomato seems to be unfavorable as a food plant for the leaf 
hopper. The variety known as Stone was used in the inoculation experiments. 
The case of goose-foot, Chenopodium murale, is of special interest in consider¬ 
ing the susceptibility of other plants. In the list previously published it was 
given as nonsusceptible. Before the time of that publication, nine experiments 
in regard to the susceptibility of C. murale had been performed. Viruliferous leaf- 
hoppers were caged on young plants in the attempt to produce the disease, or 
nymphs reared from viruliferous females on C. murale were tested on beets. The 
results of all these tests indicated that the species was not susceptible to the dis¬ 
ease. The fact may be of some significance that all these early experiments were 
made at Spreckels, Calif., where the climate is usually cool. During the year 
1919 and the two subsequent seasons, further tests were made at Riverside, Calif. 
In some instances the results were in part or entirely positive. In other words, 
Eutettix tenella nymphs reared on C. murale from viruliferous females produced 
curly-top in some or all of the plants to which they were transferred. Out of 43 
experiments, however, only 13 gave positive results. The positive results show 
that under some conditions the plant harbors the virus of curly-top. In no case 
# have clearly defined symptoms, such as swelling of the leaf veins or veinlet clear¬ 
ing, been noted, but in some of the plants a dwarfing of the later growth which 
may have been due to the disease has been observed. The fact that positive 
results were obtained in so small a proportion of the later tests and in none of 
