Apr. 26,1924 Studies on Curly- Top Disease of the Sugar Beet 
299 
turn yellow and die, while the younger central leaves which are dwarfed and 
usually show conspicuous vein swellings on the under sides remain green (PL 
2, D). The vein swellings vary with different individual plants from cases where 
practically every veinlet is irregularly swollen (PL 2, B), to cases which show 
only scattered, inconspicuous, rounded swellings (Pl. 2, A). The disease is char¬ 
acterized by a necrosis of the phloem throughout the vascular system (Pl. 3, B), 
and in the advanced stages of the disease this necrosis shows in the roots as dark 
concentric rings (Pl. 4). The exudation of a clear, viscous liquid is often con¬ 
spicuous on the oldest leaves which show the vein swellings (Pl. 2, C). 4 
DISTRIBUTION OF CURLY-TOP AND THE BEET LEAFHOPPER 
The geographical distribution of the curly-top disease is limited to the arid 
or semiarid regions of the western part of North America in which the insect 
Eutettix tenella Baker is found and to the districts adjacent to these regions. In 
general it may be said, therefore, that the disease occurs wherever this leaf hop¬ 
per is found. It has been authoritatively reported from the following States; 
Arizona, California, Colorado, Idaho, Kansas, Nebraska, New Mexico, Oregon, 
Texas, Utah, and Washington. 
The disease has been reported from practically every region in California 
in which beets are grown. The distribution of the beet leafhopper has been 
studied more extensively than has the distribution of the disease, and because of its 
significance from the standpoint of where the disease occurs of would occur if beets 
were planted the localities from which the insect has been reported are listed here. 
LOCALITIES FROM WHICH THE BEET LEAFHOPPER HAS BEEN REPORTED 
CALIFORNIA 
1. Agatha. 
36. Dos Palos. 
70. Oxnard. 
2. Allensworth. 
37. Earlimart. 
71. Pacheco Pass (entrance) 
3. Alpaugh. 
38. El Centro. 
72. Paso Robles. 
4. Altamont Pass. 
39. Famoso. 
73. Pleasanton. 
5. Alvarado. 
40. Gonzales. 
74. Prado. 
6. Angiola. 
41. Goshen Junction. 
75. Ravendale. 
7. Antelope Valley. 
42. Hamilton City. 
76. Red Bluff. 
8. Arlington. 
43. Heber. 
77* Riverside. 
9. Bakersfield. 
44. Helm. 
78. Rosamond. 
10. Barstow. 
11. Betteravia. 
45. Hemet. 
79. San Ardo. 
12 Bittftrwatpr 
46. Holtville. 
80. San Bernardino. 
X«> X V UVl TT wL'vi ■ 
13. Blanco. 
47. Huntington Beach. 
81. San Fernando Valley. 
14. Brawley. 
48. Huron. 
82. San Jacinto. 
16. Buena Vista. 
49. Imperial. 
83. San Jose. 
16. Buttonwillow. 
50. King City. 
84. San Lorenzo Creek. 
17. Calexico. 
51. Lancaster. 
85. Santa Ana. 
18. Calipatria. 
52. Le Grand. 
86. Santa Margarita. 
19. Castaic. 
53. LosAlamitos. 
87. Sargent. 
20. Castroville. 
54. Los BanSs. 
88. Saugus. 
21. Centerville. 
55. Lost Hills. 
89. Shatter. 
22. Chino. 
56. McKittrick. 
90. Soledad. 
23. Cholame. 
57. Manteca. 
91. Spence. 
24. Chowchilla. 
58. Marysville. 
92. Spreckels. 
25. Chualar. 
59. Mendota. 
93. Stockton. 
26. Claremont. 
60. Merced. 
94. Tejon Pass. 
27. Coalinga. 
61. Milpitas. 
95. Tracy. 
28. Compton. 
62. Modesto. 
96. Victorville. 
29. Connor. 
63. Mojave River. 
97. Visalia. 
30. Corcoran. 
64. Moro Cojo. 
98. Volta. 
31. Coyote Wells. 
65. Mountain View. 
99. Wasco. 
32. Crows Landing. 
66. Neenach. 
100. Watts. 
33. Davis. 
67. Niland. 
101. Westmoreland. 
34. Dixieland. 
68. Norwalk. 
102. Williams. 
35. Dominguez Junction. 
69. Oro Loma. 
103. Willowbrook. 
4 The progress of the work has been greatly aided by the use of the laboratory and field facilities of the 
Citrus Experiment Station of the University of California. The writers are indebted to the director and 
the staff for many courtesies and accommodations. 
