CONTROL OF BACTERIAL WILT 3 
Georgia, Florida, and from most of the important tobacco-growing 
regions of other countries. 
NEED OF EPPECTIY Ee CONTROL 
In experiments on wilt conducted in this country from 1903. to 
1917 (3), it was demonstrated that crop rotation was of value as a 
control measure. In the Netherlands East Indies, where experimental 
work was begun about 1890, essentially the same conclusion was drawn. 
(5, 9). These earlier experiments were the basis for the current reec- 
ommendations of crop rotation and sanitary practices for wilt control, 
measures that have been extensively used in this country. As prac- 
ticed by farmers, however, rotation reduced losses from the disease 
but could not be depended on for adequate control. Even though 
the best known control measures were used, losses as high as 90 percent 
have been experienced on some farms. Because the average loss during 
recent years was 20 percent in the badly infested areas of Granville, 
Wake, and Durham Counties, N. C., the need was great for more 
effective rotations or for other practical methods of control. 
QUTLINE OF EXPERIMENTAL WORK 
In 1935 a broad program of experimental work was instituted on 
fields near Creedmoor, N. C., in the area where wilt was first reported. 
The results of host-range studies with Bacterium solanacearum (6) and 
of development of resistant breeding stocks (7) have already been 
published. It is the purpose of this circular to report the results of 
experimental work on crop rotation and chemical treatments of the 
soil in the control of the disease. The major objective was to increase 
the effectiveness of crop rotation because of its practicability and of 
the fact that it was already in general use. It has been assumed that 
wilt control by rotation depends on the elimination of host plants and 
hence on starvation of the parasite. On more critical study it was 
apparent that other factors might play a part in the results obtained 
and therefore required investigation. The several factors considered 
were: (1) Effectiveness of rotations of the crop plants commonly 
grown in the wilt-infested area; (2) effect of recontamination of rotated 
areas on the degree of control obtained: (3) effect of a small number of 
susceptible weeds on the control obtained from an otherwise immune 
growth; (4) seasonal effects on performance of rotations; (5) length of 
rotation required for effective control; and (6) effect of rotations on 
the carry-over of infection in soil on different areas of fields. 
Less extensive experiments tested rotation in combination with 
genetic resistance and chemical treatment of the soil. In addition, 
a group of complex organic compounds were tested as soil treatments. 
The experiments included many different types of work, and the 
methods used are presented in different sections of the circular to- 
gether with the results of the various tests. 
CONTROE- BY CROP ROFATION 
The literature on the control of bacterial wilt repeatedly implies 
that the absence of susceptible plants during the rotation period 
assures a high degree of control. This supposition was based on the 
belief that the parasite would be starved out, thereby eliminating the 
